I would like some help on comprehending this question as well as a push in the right direction. The

Brenden Tran

Brenden Tran

Answered question

2022-06-11

I would like some help on comprehending this question as well as a push in the right direction. The question gave a system of first-order differential equation.
x ( t ) = 4 x ( t ) 3 y ( t ) + 6 e 2 t
y ( t ) = 4 x ( t ) 6 y ( t )
The question asked me to find the 2nd inhomogeneous equation that satisfies x(t). Does this mean the answer should all be in terms of x? I tried focusing on the x and differentiating it with respect to t.
so x ( t ) = 4 x ( t ) 3 y ( t ) + 6 e 2 t becomes:
x ( t ) = 4 x ( t ) 3 y ( t ) + 12 e 2 t
for simplicity sake, I will write x(t) as x and y(t) as y.
After that step, I replaced the y' in the x'' equation with the rearranged y' from the original question into the differentiated x' equation. This gives:
x = 4 x 3 ( 4 x 6 ( 1 3 ( x 4 x 6 e 2 t ) + 12 e 2 t
this cancels down to:
x = 4 x 12 x + 2 x 8 x
but if you move everything to one side, it becomes
x 6 x + 20 x = 0
this is a second-order homogenous equation, so I don't quite know where I went wrong

Answer & Explanation

Raven Higgins

Raven Higgins

Beginner2022-06-12Added 17 answers

n your third line you wrote the original first line but with an extra dash on the y which shouldn't be there. Although your fourth line is correct, you have substituted an incorrect expression for y' due to this error, and that's where it all went wrong...
I assume you can fix this.

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