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Edexcel FP2 - 2nd order differentiation question Watch

1. (a) Find the general solution of the differential equation
4(d2y/dy2) - (dy/dx) - 3y = x^2

[CF: Ae^((-3/4)x) + Be^x]

(b) Find the particular solution for which, x=0, y=3 and dy/dx = 5

according to the mark scheme, you start with y = px^2 + qx + r => y' = 2px + q, y'' = 2p

anyone know why you have to assume that equation for y? does it have anything to do with the x^2 in the original equation (implying a quadratic in y)?
2. (Original post by the maths guy)
(a) Find the general solution of the differential equation
4(d2y/dy2) - (dy/dx) - 3y = x^2

[CF: Ae^((-3/4)x) + Be^x]

(b) Find the particular solution for which, x=0, y=3 and dy/dx = 5

according to the mark scheme, you start with y = px^2 + qx + r => y' = 2px + q, y'' = 2p

anyone know why you have to assume that equation for y? does it have anything to do with the x^2 in the original equation (implying a quadratic in y)?
Yes, that's what I'd imagine the reasoning to be. The RHS is a quadratic and having y as a quadratic will also give you a quadratic on the LHS.
3. (Original post by Farhan.Hanif93)
Yes, that's what I'd imagine the reasoning to be.
When did you have your Cambridge interview btw?
4. (Original post by davidmarsh01)
When did you have your Cambridge interview btw?
The 8th.
5. (Original post by davidmarsh01)
When did you have your Cambridge interview btw?
Hey, how did your cam interview go?
6. (Original post by cpdavis)
Hey, how did your cam interview go?
Yeah, the interview went pretty well actually, but the test was worse Hope they liked me
7. (Original post by Farhan.Hanif93)
Yes, that's what I'd imagine the reasoning to be. The RHS is a quadratic and having y as a quadratic will also give you a quadratic on the LHS.
so if the RHS was 3x, y would be ax + b?
and if 2, y = ax?

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