Find the general solution for differential equation (d4 - 5d3 + 5d2 + 5d - 6)y = 0

Given differential equation, (D4 - 5D3 + 5D2 + 5D - 6)y = 0

=> For general solution of equation,

Solve D4 - 5D3 + 5D2 + 5D - 6 = 0

=> D4 - 5D3 + 6D2 - D2 + 5D - 6 = 0

=> D2 (D2 - 5D + 6) - (D2 - 5D + 6) = 0

=> (D2 - 5D + 6)(D2 - 1) = 0           (1)

Now 

D2  - 1 = (D - 1)(D + 1)  and 

Factors of D2 - 5D + 6

D2 - 5D + 6 = D2 - 2D - 3D + 6

= D(D - 2) - 3(D - 2)

= (D - 3)(D - 2)

Therefore, equation (1) implies

(D2 - 5D + 6)(D2 - 1) = (D - 3)(D - 2)(D - 1)(D + 1) = 0

=> D = 3, 2, 1, -1 or D = -1, 1,, 2, 3

=> General solution of differential equation is,

=> y = C1 e-x + C2 ex + C3 e2x + C4 e3x .