Solve a system of equations with $exp$ function












1












$begingroup$


I would like your help to understand whether the following system admits a unique solution for the unknowns $rho_1, rho_2, rho_0$.



$$
begin{cases}
1-t=frac{exp { rho_0+rho_1+ rho_2(1)}}{1+exp { rho_0+rho_1+ rho_2}}\
r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}
\
w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}
end{cases}
$$

$r,t,w$ are known values in $(0,1)$.



Here my incomplete attempt to simplify:



$$
begin{cases}
log(1-t)=rho_0+rho_1+ rho_2-log(1+exp { rho_0+rho_1+ rho_2})\
log(r)= rho_0+ rho_2 -log(1+exp{ rho_0+ rho_2})
\
log(w)=-log(1+exp { rho_0+rho_1+ 2rho_2})
end{cases}
$$

I'm unable to proceed.










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$endgroup$












  • $begingroup$
    Solve for $exprho_1,exprho_2,exprho_3$ and then take the natural logarithm
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 12:54
















1












$begingroup$


I would like your help to understand whether the following system admits a unique solution for the unknowns $rho_1, rho_2, rho_0$.



$$
begin{cases}
1-t=frac{exp { rho_0+rho_1+ rho_2(1)}}{1+exp { rho_0+rho_1+ rho_2}}\
r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}
\
w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}
end{cases}
$$

$r,t,w$ are known values in $(0,1)$.



Here my incomplete attempt to simplify:



$$
begin{cases}
log(1-t)=rho_0+rho_1+ rho_2-log(1+exp { rho_0+rho_1+ rho_2})\
log(r)= rho_0+ rho_2 -log(1+exp{ rho_0+ rho_2})
\
log(w)=-log(1+exp { rho_0+rho_1+ 2rho_2})
end{cases}
$$

I'm unable to proceed.










share|cite|improve this question









$endgroup$












  • $begingroup$
    Solve for $exprho_1,exprho_2,exprho_3$ and then take the natural logarithm
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 12:54














1












1








1





$begingroup$


I would like your help to understand whether the following system admits a unique solution for the unknowns $rho_1, rho_2, rho_0$.



$$
begin{cases}
1-t=frac{exp { rho_0+rho_1+ rho_2(1)}}{1+exp { rho_0+rho_1+ rho_2}}\
r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}
\
w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}
end{cases}
$$

$r,t,w$ are known values in $(0,1)$.



Here my incomplete attempt to simplify:



$$
begin{cases}
log(1-t)=rho_0+rho_1+ rho_2-log(1+exp { rho_0+rho_1+ rho_2})\
log(r)= rho_0+ rho_2 -log(1+exp{ rho_0+ rho_2})
\
log(w)=-log(1+exp { rho_0+rho_1+ 2rho_2})
end{cases}
$$

I'm unable to proceed.










share|cite|improve this question









$endgroup$




I would like your help to understand whether the following system admits a unique solution for the unknowns $rho_1, rho_2, rho_0$.



$$
begin{cases}
1-t=frac{exp { rho_0+rho_1+ rho_2(1)}}{1+exp { rho_0+rho_1+ rho_2}}\
r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}
\
w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}
end{cases}
$$

$r,t,w$ are known values in $(0,1)$.



Here my incomplete attempt to simplify:



$$
begin{cases}
log(1-t)=rho_0+rho_1+ rho_2-log(1+exp { rho_0+rho_1+ rho_2})\
log(r)= rho_0+ rho_2 -log(1+exp{ rho_0+ rho_2})
\
log(w)=-log(1+exp { rho_0+rho_1+ 2rho_2})
end{cases}
$$

I'm unable to proceed.







logarithms exponential-function systems-of-equations






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asked Dec 18 '18 at 12:33









STFSTF

691422




691422












  • $begingroup$
    Solve for $exprho_1,exprho_2,exprho_3$ and then take the natural logarithm
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 12:54


















  • $begingroup$
    Solve for $exprho_1,exprho_2,exprho_3$ and then take the natural logarithm
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 12:54
















$begingroup$
Solve for $exprho_1,exprho_2,exprho_3$ and then take the natural logarithm
$endgroup$
– Shubham Johri
Dec 18 '18 at 12:54




$begingroup$
Solve for $exprho_1,exprho_2,exprho_3$ and then take the natural logarithm
$endgroup$
– Shubham Johri
Dec 18 '18 at 12:54










1 Answer
1






active

oldest

votes


















1












$begingroup$

$displaystyle r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}impliesexp{ rho_0+ rho_2}=frac r{1-r}$



$displaystyle1-t=frac{exp { rho_0+rho_1+ rho_2}}{1+exp { rho_0+rho_1+ rho_2}}=frac{rexp{{rho_1}}}{1-r+rexp {rho_1}}impliesexp{{rho_1}}=frac{(1-r)(1-t)}{rt}$



$displaystyle w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}=frac{1}{1+exp { rho_2}cdotfrac r{1-r}cdotfrac{(1-r)(1-t)}{rt}}implies exp{{rho_2}}=frac{t(1-w)}{w(1-t)}$



$$thereforedisplaystylerho_0=lnBig[frac{rw(1-t)}{t(1-r)(1-w)}Big]$$



$$displaystylerho_1=lnBig[frac{(1-r)(1-t)}{rt}Big]$$



$$displaystylerho_2=lnBig[frac{t(1-w)}{w(1-t)}Big]$$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thanks: I think $2$ in front of $rho_2$ has been ignored in your derivations.
    $endgroup$
    – STF
    Dec 18 '18 at 13:16










  • $begingroup$
    Where exactly did I miss it?
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 14:40










  • $begingroup$
    Sorry: am I right that in the second equality for $w$ we should have $frac{1}{1+exp{2rho_2}frac{r}{1-r} frac{(1-r)(1-t)}{rt}}$?
    $endgroup$
    – STF
    Dec 18 '18 at 15:06










  • $begingroup$
    $exp{{rho_1+rho_1+2rho_2}}=exp{{rho_0+rho_1+rho_2}}cdotexp{{rho_2}}=frac{1-t}tcdotexp{{rho_2}}$. I got $exp{{rho_0+rho_1+rho_2}}$ by multiplying the expressions for $exp{{rho_0+rho_2}}$ and $exp{{rho_1}}$
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 15:09












  • $begingroup$
    I see now. Thanks
    $endgroup$
    – STF
    Dec 18 '18 at 15:19











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1 Answer
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active

oldest

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1 Answer
1






active

oldest

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active

oldest

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active

oldest

votes









1












$begingroup$

$displaystyle r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}impliesexp{ rho_0+ rho_2}=frac r{1-r}$



$displaystyle1-t=frac{exp { rho_0+rho_1+ rho_2}}{1+exp { rho_0+rho_1+ rho_2}}=frac{rexp{{rho_1}}}{1-r+rexp {rho_1}}impliesexp{{rho_1}}=frac{(1-r)(1-t)}{rt}$



$displaystyle w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}=frac{1}{1+exp { rho_2}cdotfrac r{1-r}cdotfrac{(1-r)(1-t)}{rt}}implies exp{{rho_2}}=frac{t(1-w)}{w(1-t)}$



$$thereforedisplaystylerho_0=lnBig[frac{rw(1-t)}{t(1-r)(1-w)}Big]$$



$$displaystylerho_1=lnBig[frac{(1-r)(1-t)}{rt}Big]$$



$$displaystylerho_2=lnBig[frac{t(1-w)}{w(1-t)}Big]$$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thanks: I think $2$ in front of $rho_2$ has been ignored in your derivations.
    $endgroup$
    – STF
    Dec 18 '18 at 13:16










  • $begingroup$
    Where exactly did I miss it?
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 14:40










  • $begingroup$
    Sorry: am I right that in the second equality for $w$ we should have $frac{1}{1+exp{2rho_2}frac{r}{1-r} frac{(1-r)(1-t)}{rt}}$?
    $endgroup$
    – STF
    Dec 18 '18 at 15:06










  • $begingroup$
    $exp{{rho_1+rho_1+2rho_2}}=exp{{rho_0+rho_1+rho_2}}cdotexp{{rho_2}}=frac{1-t}tcdotexp{{rho_2}}$. I got $exp{{rho_0+rho_1+rho_2}}$ by multiplying the expressions for $exp{{rho_0+rho_2}}$ and $exp{{rho_1}}$
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 15:09












  • $begingroup$
    I see now. Thanks
    $endgroup$
    – STF
    Dec 18 '18 at 15:19
















1












$begingroup$

$displaystyle r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}impliesexp{ rho_0+ rho_2}=frac r{1-r}$



$displaystyle1-t=frac{exp { rho_0+rho_1+ rho_2}}{1+exp { rho_0+rho_1+ rho_2}}=frac{rexp{{rho_1}}}{1-r+rexp {rho_1}}impliesexp{{rho_1}}=frac{(1-r)(1-t)}{rt}$



$displaystyle w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}=frac{1}{1+exp { rho_2}cdotfrac r{1-r}cdotfrac{(1-r)(1-t)}{rt}}implies exp{{rho_2}}=frac{t(1-w)}{w(1-t)}$



$$thereforedisplaystylerho_0=lnBig[frac{rw(1-t)}{t(1-r)(1-w)}Big]$$



$$displaystylerho_1=lnBig[frac{(1-r)(1-t)}{rt}Big]$$



$$displaystylerho_2=lnBig[frac{t(1-w)}{w(1-t)}Big]$$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thanks: I think $2$ in front of $rho_2$ has been ignored in your derivations.
    $endgroup$
    – STF
    Dec 18 '18 at 13:16










  • $begingroup$
    Where exactly did I miss it?
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 14:40










  • $begingroup$
    Sorry: am I right that in the second equality for $w$ we should have $frac{1}{1+exp{2rho_2}frac{r}{1-r} frac{(1-r)(1-t)}{rt}}$?
    $endgroup$
    – STF
    Dec 18 '18 at 15:06










  • $begingroup$
    $exp{{rho_1+rho_1+2rho_2}}=exp{{rho_0+rho_1+rho_2}}cdotexp{{rho_2}}=frac{1-t}tcdotexp{{rho_2}}$. I got $exp{{rho_0+rho_1+rho_2}}$ by multiplying the expressions for $exp{{rho_0+rho_2}}$ and $exp{{rho_1}}$
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 15:09












  • $begingroup$
    I see now. Thanks
    $endgroup$
    – STF
    Dec 18 '18 at 15:19














1












1








1





$begingroup$

$displaystyle r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}impliesexp{ rho_0+ rho_2}=frac r{1-r}$



$displaystyle1-t=frac{exp { rho_0+rho_1+ rho_2}}{1+exp { rho_0+rho_1+ rho_2}}=frac{rexp{{rho_1}}}{1-r+rexp {rho_1}}impliesexp{{rho_1}}=frac{(1-r)(1-t)}{rt}$



$displaystyle w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}=frac{1}{1+exp { rho_2}cdotfrac r{1-r}cdotfrac{(1-r)(1-t)}{rt}}implies exp{{rho_2}}=frac{t(1-w)}{w(1-t)}$



$$thereforedisplaystylerho_0=lnBig[frac{rw(1-t)}{t(1-r)(1-w)}Big]$$



$$displaystylerho_1=lnBig[frac{(1-r)(1-t)}{rt}Big]$$



$$displaystylerho_2=lnBig[frac{t(1-w)}{w(1-t)}Big]$$






share|cite|improve this answer









$endgroup$



$displaystyle r=frac{exp { rho_0+ rho_2 }}{1+exp{ rho_0+ rho_2}}impliesexp{ rho_0+ rho_2}=frac r{1-r}$



$displaystyle1-t=frac{exp { rho_0+rho_1+ rho_2}}{1+exp { rho_0+rho_1+ rho_2}}=frac{rexp{{rho_1}}}{1-r+rexp {rho_1}}impliesexp{{rho_1}}=frac{(1-r)(1-t)}{rt}$



$displaystyle w=frac{1}{1+exp { rho_0+rho_1+ 2rho_2}}=frac{1}{1+exp { rho_2}cdotfrac r{1-r}cdotfrac{(1-r)(1-t)}{rt}}implies exp{{rho_2}}=frac{t(1-w)}{w(1-t)}$



$$thereforedisplaystylerho_0=lnBig[frac{rw(1-t)}{t(1-r)(1-w)}Big]$$



$$displaystylerho_1=lnBig[frac{(1-r)(1-t)}{rt}Big]$$



$$displaystylerho_2=lnBig[frac{t(1-w)}{w(1-t)}Big]$$







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 18 '18 at 12:53









Shubham JohriShubham Johri

5,427818




5,427818












  • $begingroup$
    Thanks: I think $2$ in front of $rho_2$ has been ignored in your derivations.
    $endgroup$
    – STF
    Dec 18 '18 at 13:16










  • $begingroup$
    Where exactly did I miss it?
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 14:40










  • $begingroup$
    Sorry: am I right that in the second equality for $w$ we should have $frac{1}{1+exp{2rho_2}frac{r}{1-r} frac{(1-r)(1-t)}{rt}}$?
    $endgroup$
    – STF
    Dec 18 '18 at 15:06










  • $begingroup$
    $exp{{rho_1+rho_1+2rho_2}}=exp{{rho_0+rho_1+rho_2}}cdotexp{{rho_2}}=frac{1-t}tcdotexp{{rho_2}}$. I got $exp{{rho_0+rho_1+rho_2}}$ by multiplying the expressions for $exp{{rho_0+rho_2}}$ and $exp{{rho_1}}$
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 15:09












  • $begingroup$
    I see now. Thanks
    $endgroup$
    – STF
    Dec 18 '18 at 15:19


















  • $begingroup$
    Thanks: I think $2$ in front of $rho_2$ has been ignored in your derivations.
    $endgroup$
    – STF
    Dec 18 '18 at 13:16










  • $begingroup$
    Where exactly did I miss it?
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 14:40










  • $begingroup$
    Sorry: am I right that in the second equality for $w$ we should have $frac{1}{1+exp{2rho_2}frac{r}{1-r} frac{(1-r)(1-t)}{rt}}$?
    $endgroup$
    – STF
    Dec 18 '18 at 15:06










  • $begingroup$
    $exp{{rho_1+rho_1+2rho_2}}=exp{{rho_0+rho_1+rho_2}}cdotexp{{rho_2}}=frac{1-t}tcdotexp{{rho_2}}$. I got $exp{{rho_0+rho_1+rho_2}}$ by multiplying the expressions for $exp{{rho_0+rho_2}}$ and $exp{{rho_1}}$
    $endgroup$
    – Shubham Johri
    Dec 18 '18 at 15:09












  • $begingroup$
    I see now. Thanks
    $endgroup$
    – STF
    Dec 18 '18 at 15:19
















$begingroup$
Thanks: I think $2$ in front of $rho_2$ has been ignored in your derivations.
$endgroup$
– STF
Dec 18 '18 at 13:16




$begingroup$
Thanks: I think $2$ in front of $rho_2$ has been ignored in your derivations.
$endgroup$
– STF
Dec 18 '18 at 13:16












$begingroup$
Where exactly did I miss it?
$endgroup$
– Shubham Johri
Dec 18 '18 at 14:40




$begingroup$
Where exactly did I miss it?
$endgroup$
– Shubham Johri
Dec 18 '18 at 14:40












$begingroup$
Sorry: am I right that in the second equality for $w$ we should have $frac{1}{1+exp{2rho_2}frac{r}{1-r} frac{(1-r)(1-t)}{rt}}$?
$endgroup$
– STF
Dec 18 '18 at 15:06




$begingroup$
Sorry: am I right that in the second equality for $w$ we should have $frac{1}{1+exp{2rho_2}frac{r}{1-r} frac{(1-r)(1-t)}{rt}}$?
$endgroup$
– STF
Dec 18 '18 at 15:06












$begingroup$
$exp{{rho_1+rho_1+2rho_2}}=exp{{rho_0+rho_1+rho_2}}cdotexp{{rho_2}}=frac{1-t}tcdotexp{{rho_2}}$. I got $exp{{rho_0+rho_1+rho_2}}$ by multiplying the expressions for $exp{{rho_0+rho_2}}$ and $exp{{rho_1}}$
$endgroup$
– Shubham Johri
Dec 18 '18 at 15:09






$begingroup$
$exp{{rho_1+rho_1+2rho_2}}=exp{{rho_0+rho_1+rho_2}}cdotexp{{rho_2}}=frac{1-t}tcdotexp{{rho_2}}$. I got $exp{{rho_0+rho_1+rho_2}}$ by multiplying the expressions for $exp{{rho_0+rho_2}}$ and $exp{{rho_1}}$
$endgroup$
– Shubham Johri
Dec 18 '18 at 15:09














$begingroup$
I see now. Thanks
$endgroup$
– STF
Dec 18 '18 at 15:19




$begingroup$
I see now. Thanks
$endgroup$
– STF
Dec 18 '18 at 15:19


















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