Non-linear differential equation with variable coefficient

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Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.
differential-equations
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Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.
differential-equations
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up vote
1
down vote
favorite
up vote
1
down vote
favorite
Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.
differential-equations
Given $$ xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$ What is the value of $x(2)$? I tried with $dx/dt=y, dy/dt=(dy/dx)(dx/dt)$ but failed at integration.
differential-equations
asked Aug 24 at 0:10
Purushothaman
1956
1956
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4 Answers
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Even if this is not a direct answer but it leads to the answer.
This equation can be written as
$$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
Therfore $ quad xdfracdxdt=ce^t $
Then
$$ int x dx = int ce^t dt$$
so $$frac12x^2(t)=ce^t+d$$
Can you take it from here?
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up vote
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You can divide the equation by $xdotx$ and integrate the equation (chain rule).
$$ fracddotxdotx + fracdotxx = 1 $$
$$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$
$$ implies xdotx = ke^t $$
The last equation is separable again.
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Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
begineqnarray*
fracdpdx=fracx-px
endeqnarray*
or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.
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$$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
$$xx''+(x')^2=x'x$$
$$implies (x'x)'=x'x$$
Substitute $z=x'x$
$$z'= z$$
This last equation is separable...
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
accepted
Even if this is not a direct answer but it leads to the answer.
This equation can be written as
$$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
Therfore $ quad xdfracdxdt=ce^t $
Then
$$ int x dx = int ce^t dt$$
so $$frac12x^2(t)=ce^t+d$$
Can you take it from here?
add a comment |Â
up vote
3
down vote
accepted
Even if this is not a direct answer but it leads to the answer.
This equation can be written as
$$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
Therfore $ quad xdfracdxdt=ce^t $
Then
$$ int x dx = int ce^t dt$$
so $$frac12x^2(t)=ce^t+d$$
Can you take it from here?
add a comment |Â
up vote
3
down vote
accepted
up vote
3
down vote
accepted
Even if this is not a direct answer but it leads to the answer.
This equation can be written as
$$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
Therfore $ quad xdfracdxdt=ce^t $
Then
$$ int x dx = int ce^t dt$$
so $$frac12x^2(t)=ce^t+d$$
Can you take it from here?
Even if this is not a direct answer but it leads to the answer.
This equation can be written as
$$ dfracddt left( xdfracdxdt right)=xdfracdxdt,quad $$
Therfore $ quad xdfracdxdt=ce^t $
Then
$$ int x dx = int ce^t dt$$
so $$frac12x^2(t)=ce^t+d$$
Can you take it from here?
answered Aug 24 at 0:33
The_lost
1,057318
1,057318
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up vote
1
down vote
You can divide the equation by $xdotx$ and integrate the equation (chain rule).
$$ fracddotxdotx + fracdotxx = 1 $$
$$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$
$$ implies xdotx = ke^t $$
The last equation is separable again.
add a comment |Â
up vote
1
down vote
You can divide the equation by $xdotx$ and integrate the equation (chain rule).
$$ fracddotxdotx + fracdotxx = 1 $$
$$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$
$$ implies xdotx = ke^t $$
The last equation is separable again.
add a comment |Â
up vote
1
down vote
up vote
1
down vote
You can divide the equation by $xdotx$ and integrate the equation (chain rule).
$$ fracddotxdotx + fracdotxx = 1 $$
$$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$
$$ implies xdotx = ke^t $$
The last equation is separable again.
You can divide the equation by $xdotx$ and integrate the equation (chain rule).
$$ fracddotxdotx + fracdotxx = 1 $$
$$ implies ln(dotx) + ln(x) = ln(xdotx) = t+ c $$
$$ implies xdotx = ke^t $$
The last equation is separable again.
answered Aug 24 at 1:05
zaphodxvii
1068
1068
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up vote
0
down vote
Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
begineqnarray*
fracdpdx=fracx-px
endeqnarray*
or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.
add a comment |Â
up vote
0
down vote
Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
begineqnarray*
fracdpdx=fracx-px
endeqnarray*
or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
begineqnarray*
fracdpdx=fracx-px
endeqnarray*
or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.
Let$p=fracdxdt$ then $fracd^2xdt^2=p fracdpdx$ and the equation becomes
begineqnarray*
fracdpdx=fracx-px
endeqnarray*
or $p=0$. The equation above is easily solved by the substitution $p=xu$ ... good luck.
answered Aug 24 at 0:21
Donald Splutterwit
21.4k21243
21.4k21243
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$$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
$$xx''+(x')^2=x'x$$
$$implies (x'x)'=x'x$$
Substitute $z=x'x$
$$z'= z$$
This last equation is separable...
add a comment |Â
up vote
0
down vote
$$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
$$xx''+(x')^2=x'x$$
$$implies (x'x)'=x'x$$
Substitute $z=x'x$
$$z'= z$$
This last equation is separable...
add a comment |Â
up vote
0
down vote
up vote
0
down vote
$$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
$$xx''+(x')^2=x'x$$
$$implies (x'x)'=x'x$$
Substitute $z=x'x$
$$z'= z$$
This last equation is separable...
$$xdfracd^2xdt^2+left (dfracdxdtright )^2=xdfracdxdt,quad x(0)=0, x(1)=1.$$
$$xx''+(x')^2=x'x$$
$$implies (x'x)'=x'x$$
Substitute $z=x'x$
$$z'= z$$
This last equation is separable...
answered Aug 24 at 11:08
Isham
10.9k3929
10.9k3929
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