1. The problem statement, all variables and given/known data y′′=−20⋅4x^3 2. Relevant equations Undetermined coefficients method 3. The attempt at a solution so at first, solving the associated homogeneous equation I find the fundamental set of solutions to be: y1=1 and y2=x. I know that these are correct. Now for the part that confuses me. I'm trying to find Yp, the particular solution. g(x) = -80x^3 so Yp is of the form Ax^3 + Bx^2 + Cx + D but when I solve this I get Yp=0, that is not correct. It seems to me that Ax^3+Bx^2+Cx+D is Linearly independent from y1 and y2 so why doesn't this work? The book lists the solution as Yp=-4x^5.