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how to solve a system of diff eq ? - hpfx - 05-01-2016 09:14 AM

I try to solve this small system of differential equation :


with initial conds : x(0)=0 and y(0)=1

I tried with desolve on 10077,
something like that desolve({x'+y=t^2, x'+y'=6} and x(0)=0 and y(0)=1, {x,y})
but I didn't get any result.

does someone knows how to do ?

RE: how to solve a system of diff eq ? - roadrunner - 05-01-2016 10:30 AM

Three points:

1. I solved the second equation for x', plug it into the first equation, and solved for x and y separately;
2. I think you have to tell desolve that t is the time variable or it assumes x;
3. I have never had luck typing y'. Typing diff(y) seems to work better.

Here's the code:

desolve(((6-(y')+y) = (t^2)) AND ((y(0)) = 1),t,y)
returns y:

returns y':

desolve(((x'+5*e^t+2*t+2) = 6) AND ((x(0)) = 0),t,x)
returns x:

RE: how to solve a system of diff eq ? - parisse - 05-01-2016 11:39 AM

desolve solves differential equations, not systems, except for linear systems with constant coefficient for the homogeneous part, then the syntax is
desolve(y'=A*y+b) where A is the matrix and b a vector (second member)