Question

this one is tricky. help please!

y''-4y'+3y=2cosx+4sinx

i'm having trouble getting the Yp!

Answer 1

You can try substituting y = asinx + bcosx

Answer 2

why would that help. I'm in diff eq as well and I wasn't thinking about that.

Answer 3

its called th method of undetermined coefficients

Answer 4

put it on the left side....compare with coeffs on the right fr etermining a a and b

Answer 5

isn't it

y=a cos x + b sinx + cx cos x + dx sin x

Answer 6

that is for a special case i think

Answer 7

what are the roots anyway?
+i, -i

aren't they like, twice? then it will be case 4?

Answer 8

r^2 - 4r +3 = 0
(r - 3)(r-1)
r= 3, 1

Answer 9

that is for the homo part

Answer 10

im telling you
take y=asinx + bcosx
substitute y'' and y' and y in the above eqn and compare LHS and RHS
ull get 2 eqns in a and b
determine a and b and you have your soln

Answer 11

i did that, i always get 0 for B. it's not supposed to be the answer.

Answer 12

im getting the answer as b=1, a=0
which means y=cos x
y=cos x satisfies the above eqns

Answer 13

oh sorry. i looked at the wrong answer on my book. i am sorry. Our answer is right. Thank you!

Answer 14

Your welcome