Set up the appropriate form of a solution yp of y^(3)+y'' = 4x^2 , but DO NOT determine the values of the coefficients.

guy this is what i have done so far

DE : y^(3)+y'' = 4x^2

CE: r^3 + r'' = 0

r1 = 0, r2= 0 , r3= -1

yc = C1 + C2x + C3 e^-x

now here i am confuse about what to do to guess yp. should yp be Ax^2?? plz help me understand this