How to antidifferentiate with a negative exponent?
$begingroup$
$6x^{-2} + 2x^{-4} -3x^{-3}$.
How would the anti diff process work for fractions? I have $frac{1}{6x^2}$ for the first part. Am I supposed to add one to x, and then put it all over 3? How would the fraction then resolve?
calculus
$endgroup$
add a comment |
$begingroup$
$6x^{-2} + 2x^{-4} -3x^{-3}$.
How would the anti diff process work for fractions? I have $frac{1}{6x^2}$ for the first part. Am I supposed to add one to x, and then put it all over 3? How would the fraction then resolve?
calculus
$endgroup$
add a comment |
$begingroup$
$6x^{-2} + 2x^{-4} -3x^{-3}$.
How would the anti diff process work for fractions? I have $frac{1}{6x^2}$ for the first part. Am I supposed to add one to x, and then put it all over 3? How would the fraction then resolve?
calculus
$endgroup$
$6x^{-2} + 2x^{-4} -3x^{-3}$.
How would the anti diff process work for fractions? I have $frac{1}{6x^2}$ for the first part. Am I supposed to add one to x, and then put it all over 3? How would the fraction then resolve?
calculus
calculus
asked May 9 '16 at 13:51
user6050977user6050977
1658
1658
add a comment |
add a comment |
4 Answers
4
active
oldest
votes
$begingroup$
Hint. A general rule, working for all exponents (both negative and non-negative):
$$
f(x)=x^{alpha} quad text{gives an antiderivative } , F(x)=frac{x^{alpha+1}}{alpha+1}+C quad text{if} quad alpha neq-1,
$$
$$
f(x)=x^{-1}= frac1xquad text{gives an antiderivative } , F(x)=ln (x)+C quad text{if} quad x>0,
$$
where $C$ is any constant.
$endgroup$
add a comment |
$begingroup$
Two general formulas:
$(x^n)' = n cdot x^{n-1}$ (for any integer $n neq 0$)
$(c cdot f(x))' = c cdot f'(x)$ (for any number $c$)
So we know that: $(x^{-1})' = -1 cdot x^{-2}$
So: $(-6 cdot x^{-1})' = -6 cdot (-1) cdot x^{-2} = 6 cdot x^{-2}$
So the antiderivative of $6 cdot x^{-2}$ is $-6 cdot x^{-1}$.
$endgroup$
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
@user6050977 That's correct.
$endgroup$
– peter.petrov
May 9 '16 at 20:15
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:50
$begingroup$
Yes. I don't understand what you don't understand. Just sit down and write it slowly and think about it, using the formulas on this page.
$endgroup$
– peter.petrov
May 10 '16 at 10:42
add a comment |
$begingroup$
Just continue to use the rule $(x^{n})'=nx^{n-1}$ for all $nin mathbb{Z}$, $nnot=0$. Hence,
$(x^{-1})'=-x^{-2}implies(-6x^{-1})'=6x^{-2}$.
$(x^{-3})'=-3x^{-4}implies(-frac{2}{3}x^{-3})'=2x^{-4}$.
$(x^{-2})'=-2x^{-3}implies(frac{3}{2}x^{-2})'=-3x^{-3}$.
So, the antiderivative is: $-6x^{-1}-frac{2}{3}x^{-3}+frac{3}{2}x^{-2}$.
$endgroup$
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
Yes. The exponents you have are $-2, -4, -3$. When you add one to each of them, you get $-1, -3, -2$.
$endgroup$
– ervx
May 9 '16 at 19:11
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:49
$begingroup$
You have $6/x^{2}=6x^{-2}$. Add $1$ to the exponent and consider $x^{-1}$. We have that $(x^{-1})'=-x^{-2}$, but we need something whose derivative is $6x^{-2}$, so, since $(x^{-1})'=-x^{-2}$, it must be that $(-6x^{-1})'=6x^{-2}$.
$endgroup$
– ervx
May 10 '16 at 13:34
add a comment |
$begingroup$
I think your confusion comes from missing this:
$frac{1}{x^2}=x^{-2}$
$frac{1}{x^3}=x^{-3}$
$frac{1}{x^4}=x^{-4}$
Just proceed as you would for positive powers, but being careful about minus signs.
$frac{1}{x}=x^{-1} $ is a special case since you can't get it by differentiating $x^0$ (try it!) but they've very kindly avoided putting that in the expression.
Example:
Find the antiderivative of $frac{2}{x^5}$.
First write this as $$frac{2}{x^5}=2x^{-5}$$
Thinking of this as $2x^{n}$, what is $n$? $$n=-5$$
So, what is $n+1$? $$n+1=-4$$
In which case, what is $frac{x^{n+1}}{n+1}$?
$$frac{x^{n+1}}{n+1}=frac{x^{-4}}{-4} = -frac{1}{4{x^4}}$$
But we wanted the antiderivative of $2x^{-5}$, not just $x^{-5}$, so we still need to multiply by 2 and we finally get $$2left(-frac{1}{4{x^4}}right)=-frac{1}{2{x^4}}$$
$endgroup$
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Hint. A general rule, working for all exponents (both negative and non-negative):
$$
f(x)=x^{alpha} quad text{gives an antiderivative } , F(x)=frac{x^{alpha+1}}{alpha+1}+C quad text{if} quad alpha neq-1,
$$
$$
f(x)=x^{-1}= frac1xquad text{gives an antiderivative } , F(x)=ln (x)+C quad text{if} quad x>0,
$$
where $C$ is any constant.
$endgroup$
add a comment |
$begingroup$
Hint. A general rule, working for all exponents (both negative and non-negative):
$$
f(x)=x^{alpha} quad text{gives an antiderivative } , F(x)=frac{x^{alpha+1}}{alpha+1}+C quad text{if} quad alpha neq-1,
$$
$$
f(x)=x^{-1}= frac1xquad text{gives an antiderivative } , F(x)=ln (x)+C quad text{if} quad x>0,
$$
where $C$ is any constant.
$endgroup$
add a comment |
$begingroup$
Hint. A general rule, working for all exponents (both negative and non-negative):
$$
f(x)=x^{alpha} quad text{gives an antiderivative } , F(x)=frac{x^{alpha+1}}{alpha+1}+C quad text{if} quad alpha neq-1,
$$
$$
f(x)=x^{-1}= frac1xquad text{gives an antiderivative } , F(x)=ln (x)+C quad text{if} quad x>0,
$$
where $C$ is any constant.
$endgroup$
Hint. A general rule, working for all exponents (both negative and non-negative):
$$
f(x)=x^{alpha} quad text{gives an antiderivative } , F(x)=frac{x^{alpha+1}}{alpha+1}+C quad text{if} quad alpha neq-1,
$$
$$
f(x)=x^{-1}= frac1xquad text{gives an antiderivative } , F(x)=ln (x)+C quad text{if} quad x>0,
$$
where $C$ is any constant.
edited Nov 29 '18 at 21:35
Brahadeesh
6,19742361
6,19742361
answered May 9 '16 at 14:01
Olivier OloaOlivier Oloa
108k17176293
108k17176293
add a comment |
add a comment |
$begingroup$
Two general formulas:
$(x^n)' = n cdot x^{n-1}$ (for any integer $n neq 0$)
$(c cdot f(x))' = c cdot f'(x)$ (for any number $c$)
So we know that: $(x^{-1})' = -1 cdot x^{-2}$
So: $(-6 cdot x^{-1})' = -6 cdot (-1) cdot x^{-2} = 6 cdot x^{-2}$
So the antiderivative of $6 cdot x^{-2}$ is $-6 cdot x^{-1}$.
$endgroup$
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
@user6050977 That's correct.
$endgroup$
– peter.petrov
May 9 '16 at 20:15
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:50
$begingroup$
Yes. I don't understand what you don't understand. Just sit down and write it slowly and think about it, using the formulas on this page.
$endgroup$
– peter.petrov
May 10 '16 at 10:42
add a comment |
$begingroup$
Two general formulas:
$(x^n)' = n cdot x^{n-1}$ (for any integer $n neq 0$)
$(c cdot f(x))' = c cdot f'(x)$ (for any number $c$)
So we know that: $(x^{-1})' = -1 cdot x^{-2}$
So: $(-6 cdot x^{-1})' = -6 cdot (-1) cdot x^{-2} = 6 cdot x^{-2}$
So the antiderivative of $6 cdot x^{-2}$ is $-6 cdot x^{-1}$.
$endgroup$
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
@user6050977 That's correct.
$endgroup$
– peter.petrov
May 9 '16 at 20:15
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:50
$begingroup$
Yes. I don't understand what you don't understand. Just sit down and write it slowly and think about it, using the formulas on this page.
$endgroup$
– peter.petrov
May 10 '16 at 10:42
add a comment |
$begingroup$
Two general formulas:
$(x^n)' = n cdot x^{n-1}$ (for any integer $n neq 0$)
$(c cdot f(x))' = c cdot f'(x)$ (for any number $c$)
So we know that: $(x^{-1})' = -1 cdot x^{-2}$
So: $(-6 cdot x^{-1})' = -6 cdot (-1) cdot x^{-2} = 6 cdot x^{-2}$
So the antiderivative of $6 cdot x^{-2}$ is $-6 cdot x^{-1}$.
$endgroup$
Two general formulas:
$(x^n)' = n cdot x^{n-1}$ (for any integer $n neq 0$)
$(c cdot f(x))' = c cdot f'(x)$ (for any number $c$)
So we know that: $(x^{-1})' = -1 cdot x^{-2}$
So: $(-6 cdot x^{-1})' = -6 cdot (-1) cdot x^{-2} = 6 cdot x^{-2}$
So the antiderivative of $6 cdot x^{-2}$ is $-6 cdot x^{-1}$.
edited May 9 '16 at 14:01
answered May 9 '16 at 13:54
peter.petrovpeter.petrov
5,417821
5,417821
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
@user6050977 That's correct.
$endgroup$
– peter.petrov
May 9 '16 at 20:15
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:50
$begingroup$
Yes. I don't understand what you don't understand. Just sit down and write it slowly and think about it, using the formulas on this page.
$endgroup$
– peter.petrov
May 10 '16 at 10:42
add a comment |
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
@user6050977 That's correct.
$endgroup$
– peter.petrov
May 9 '16 at 20:15
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:50
$begingroup$
Yes. I don't understand what you don't understand. Just sit down and write it slowly and think about it, using the formulas on this page.
$endgroup$
– peter.petrov
May 10 '16 at 10:42
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
1
$begingroup$
@user6050977 That's correct.
$endgroup$
– peter.petrov
May 9 '16 at 20:15
$begingroup$
@user6050977 That's correct.
$endgroup$
– peter.petrov
May 9 '16 at 20:15
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:50
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:50
$begingroup$
Yes. I don't understand what you don't understand. Just sit down and write it slowly and think about it, using the formulas on this page.
$endgroup$
– peter.petrov
May 10 '16 at 10:42
$begingroup$
Yes. I don't understand what you don't understand. Just sit down and write it slowly and think about it, using the formulas on this page.
$endgroup$
– peter.petrov
May 10 '16 at 10:42
add a comment |
$begingroup$
Just continue to use the rule $(x^{n})'=nx^{n-1}$ for all $nin mathbb{Z}$, $nnot=0$. Hence,
$(x^{-1})'=-x^{-2}implies(-6x^{-1})'=6x^{-2}$.
$(x^{-3})'=-3x^{-4}implies(-frac{2}{3}x^{-3})'=2x^{-4}$.
$(x^{-2})'=-2x^{-3}implies(frac{3}{2}x^{-2})'=-3x^{-3}$.
So, the antiderivative is: $-6x^{-1}-frac{2}{3}x^{-3}+frac{3}{2}x^{-2}$.
$endgroup$
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
Yes. The exponents you have are $-2, -4, -3$. When you add one to each of them, you get $-1, -3, -2$.
$endgroup$
– ervx
May 9 '16 at 19:11
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:49
$begingroup$
You have $6/x^{2}=6x^{-2}$. Add $1$ to the exponent and consider $x^{-1}$. We have that $(x^{-1})'=-x^{-2}$, but we need something whose derivative is $6x^{-2}$, so, since $(x^{-1})'=-x^{-2}$, it must be that $(-6x^{-1})'=6x^{-2}$.
$endgroup$
– ervx
May 10 '16 at 13:34
add a comment |
$begingroup$
Just continue to use the rule $(x^{n})'=nx^{n-1}$ for all $nin mathbb{Z}$, $nnot=0$. Hence,
$(x^{-1})'=-x^{-2}implies(-6x^{-1})'=6x^{-2}$.
$(x^{-3})'=-3x^{-4}implies(-frac{2}{3}x^{-3})'=2x^{-4}$.
$(x^{-2})'=-2x^{-3}implies(frac{3}{2}x^{-2})'=-3x^{-3}$.
So, the antiderivative is: $-6x^{-1}-frac{2}{3}x^{-3}+frac{3}{2}x^{-2}$.
$endgroup$
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
Yes. The exponents you have are $-2, -4, -3$. When you add one to each of them, you get $-1, -3, -2$.
$endgroup$
– ervx
May 9 '16 at 19:11
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:49
$begingroup$
You have $6/x^{2}=6x^{-2}$. Add $1$ to the exponent and consider $x^{-1}$. We have that $(x^{-1})'=-x^{-2}$, but we need something whose derivative is $6x^{-2}$, so, since $(x^{-1})'=-x^{-2}$, it must be that $(-6x^{-1})'=6x^{-2}$.
$endgroup$
– ervx
May 10 '16 at 13:34
add a comment |
$begingroup$
Just continue to use the rule $(x^{n})'=nx^{n-1}$ for all $nin mathbb{Z}$, $nnot=0$. Hence,
$(x^{-1})'=-x^{-2}implies(-6x^{-1})'=6x^{-2}$.
$(x^{-3})'=-3x^{-4}implies(-frac{2}{3}x^{-3})'=2x^{-4}$.
$(x^{-2})'=-2x^{-3}implies(frac{3}{2}x^{-2})'=-3x^{-3}$.
So, the antiderivative is: $-6x^{-1}-frac{2}{3}x^{-3}+frac{3}{2}x^{-2}$.
$endgroup$
Just continue to use the rule $(x^{n})'=nx^{n-1}$ for all $nin mathbb{Z}$, $nnot=0$. Hence,
$(x^{-1})'=-x^{-2}implies(-6x^{-1})'=6x^{-2}$.
$(x^{-3})'=-3x^{-4}implies(-frac{2}{3}x^{-3})'=2x^{-4}$.
$(x^{-2})'=-2x^{-3}implies(frac{3}{2}x^{-2})'=-3x^{-3}$.
So, the antiderivative is: $-6x^{-1}-frac{2}{3}x^{-3}+frac{3}{2}x^{-2}$.
answered May 9 '16 at 14:01
ervxervx
10.3k31338
10.3k31338
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
Yes. The exponents you have are $-2, -4, -3$. When you add one to each of them, you get $-1, -3, -2$.
$endgroup$
– ervx
May 9 '16 at 19:11
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:49
$begingroup$
You have $6/x^{2}=6x^{-2}$. Add $1$ to the exponent and consider $x^{-1}$. We have that $(x^{-1})'=-x^{-2}$, but we need something whose derivative is $6x^{-2}$, so, since $(x^{-1})'=-x^{-2}$, it must be that $(-6x^{-1})'=6x^{-2}$.
$endgroup$
– ervx
May 10 '16 at 13:34
add a comment |
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
$begingroup$
Yes. The exponents you have are $-2, -4, -3$. When you add one to each of them, you get $-1, -3, -2$.
$endgroup$
– ervx
May 9 '16 at 19:11
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:49
$begingroup$
You have $6/x^{2}=6x^{-2}$. Add $1$ to the exponent and consider $x^{-1}$. We have that $(x^{-1})'=-x^{-2}$, but we need something whose derivative is $6x^{-2}$, so, since $(x^{-1})'=-x^{-2}$, it must be that $(-6x^{-1})'=6x^{-2}$.
$endgroup$
– ervx
May 10 '16 at 13:34
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
$begingroup$
Isn't subtracting from an exponent supposed to be for differentiating? And adding one to an exponent for antidifferentiating?
$endgroup$
– user6050977
May 9 '16 at 17:24
1
1
$begingroup$
Yes. The exponents you have are $-2, -4, -3$. When you add one to each of them, you get $-1, -3, -2$.
$endgroup$
– ervx
May 9 '16 at 19:11
$begingroup$
Yes. The exponents you have are $-2, -4, -3$. When you add one to each of them, you get $-1, -3, -2$.
$endgroup$
– ervx
May 9 '16 at 19:11
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:49
$begingroup$
I don.t understand. So, it's $6 / x^2$? Then add one to x for $x^{-1}$, then dividing by that same -1, for $-6x^{-1}$?
$endgroup$
– user6050977
May 10 '16 at 9:49
$begingroup$
You have $6/x^{2}=6x^{-2}$. Add $1$ to the exponent and consider $x^{-1}$. We have that $(x^{-1})'=-x^{-2}$, but we need something whose derivative is $6x^{-2}$, so, since $(x^{-1})'=-x^{-2}$, it must be that $(-6x^{-1})'=6x^{-2}$.
$endgroup$
– ervx
May 10 '16 at 13:34
$begingroup$
You have $6/x^{2}=6x^{-2}$. Add $1$ to the exponent and consider $x^{-1}$. We have that $(x^{-1})'=-x^{-2}$, but we need something whose derivative is $6x^{-2}$, so, since $(x^{-1})'=-x^{-2}$, it must be that $(-6x^{-1})'=6x^{-2}$.
$endgroup$
– ervx
May 10 '16 at 13:34
add a comment |
$begingroup$
I think your confusion comes from missing this:
$frac{1}{x^2}=x^{-2}$
$frac{1}{x^3}=x^{-3}$
$frac{1}{x^4}=x^{-4}$
Just proceed as you would for positive powers, but being careful about minus signs.
$frac{1}{x}=x^{-1} $ is a special case since you can't get it by differentiating $x^0$ (try it!) but they've very kindly avoided putting that in the expression.
Example:
Find the antiderivative of $frac{2}{x^5}$.
First write this as $$frac{2}{x^5}=2x^{-5}$$
Thinking of this as $2x^{n}$, what is $n$? $$n=-5$$
So, what is $n+1$? $$n+1=-4$$
In which case, what is $frac{x^{n+1}}{n+1}$?
$$frac{x^{n+1}}{n+1}=frac{x^{-4}}{-4} = -frac{1}{4{x^4}}$$
But we wanted the antiderivative of $2x^{-5}$, not just $x^{-5}$, so we still need to multiply by 2 and we finally get $$2left(-frac{1}{4{x^4}}right)=-frac{1}{2{x^4}}$$
$endgroup$
add a comment |
$begingroup$
I think your confusion comes from missing this:
$frac{1}{x^2}=x^{-2}$
$frac{1}{x^3}=x^{-3}$
$frac{1}{x^4}=x^{-4}$
Just proceed as you would for positive powers, but being careful about minus signs.
$frac{1}{x}=x^{-1} $ is a special case since you can't get it by differentiating $x^0$ (try it!) but they've very kindly avoided putting that in the expression.
Example:
Find the antiderivative of $frac{2}{x^5}$.
First write this as $$frac{2}{x^5}=2x^{-5}$$
Thinking of this as $2x^{n}$, what is $n$? $$n=-5$$
So, what is $n+1$? $$n+1=-4$$
In which case, what is $frac{x^{n+1}}{n+1}$?
$$frac{x^{n+1}}{n+1}=frac{x^{-4}}{-4} = -frac{1}{4{x^4}}$$
But we wanted the antiderivative of $2x^{-5}$, not just $x^{-5}$, so we still need to multiply by 2 and we finally get $$2left(-frac{1}{4{x^4}}right)=-frac{1}{2{x^4}}$$
$endgroup$
add a comment |
$begingroup$
I think your confusion comes from missing this:
$frac{1}{x^2}=x^{-2}$
$frac{1}{x^3}=x^{-3}$
$frac{1}{x^4}=x^{-4}$
Just proceed as you would for positive powers, but being careful about minus signs.
$frac{1}{x}=x^{-1} $ is a special case since you can't get it by differentiating $x^0$ (try it!) but they've very kindly avoided putting that in the expression.
Example:
Find the antiderivative of $frac{2}{x^5}$.
First write this as $$frac{2}{x^5}=2x^{-5}$$
Thinking of this as $2x^{n}$, what is $n$? $$n=-5$$
So, what is $n+1$? $$n+1=-4$$
In which case, what is $frac{x^{n+1}}{n+1}$?
$$frac{x^{n+1}}{n+1}=frac{x^{-4}}{-4} = -frac{1}{4{x^4}}$$
But we wanted the antiderivative of $2x^{-5}$, not just $x^{-5}$, so we still need to multiply by 2 and we finally get $$2left(-frac{1}{4{x^4}}right)=-frac{1}{2{x^4}}$$
$endgroup$
I think your confusion comes from missing this:
$frac{1}{x^2}=x^{-2}$
$frac{1}{x^3}=x^{-3}$
$frac{1}{x^4}=x^{-4}$
Just proceed as you would for positive powers, but being careful about minus signs.
$frac{1}{x}=x^{-1} $ is a special case since you can't get it by differentiating $x^0$ (try it!) but they've very kindly avoided putting that in the expression.
Example:
Find the antiderivative of $frac{2}{x^5}$.
First write this as $$frac{2}{x^5}=2x^{-5}$$
Thinking of this as $2x^{n}$, what is $n$? $$n=-5$$
So, what is $n+1$? $$n+1=-4$$
In which case, what is $frac{x^{n+1}}{n+1}$?
$$frac{x^{n+1}}{n+1}=frac{x^{-4}}{-4} = -frac{1}{4{x^4}}$$
But we wanted the antiderivative of $2x^{-5}$, not just $x^{-5}$, so we still need to multiply by 2 and we finally get $$2left(-frac{1}{4{x^4}}right)=-frac{1}{2{x^4}}$$
edited Nov 30 '18 at 0:07
answered Nov 29 '18 at 22:19
timtfjtimtfj
1,318318
1,318318
add a comment |
add a comment |
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