FE-3

[Victor Ivrii]

\begin{equation*}
y^{(4)} -3y''-4y = \sin (t)+8 t.
\end{equation*}

[Jason Hamilton]

solve homogeneous->  roots are i,-i,2,-2

Yh=c1 e^2t +c2 e^-2t +c3 cost +c4 sint

Yp-> undetermined coefficients-> Yp= Atcost +Btsint +Ct +D

evaulate polynomial terms => C=-2. D=0

evaulate sinusoidal terms => A=1/10 B=0

Y= c1 e^2t +c2 e^-2t +c3 cost +c4 sint + (1/10)tcost -2t

[Jason Hamilton]

Also, I MIGHT have used 'x' instead of 't' on the test, would I lose marks if I used the wrong variable?

[Victor Lam]

i did this

[Benny Ho]

Solutions

[Victor Ivrii]

Benny, WTH you posted Q1 into FE-3 and Q3 into FE-1 (so I needed to split and merge)?