When the polynomial P(x) = x3 + 3x2 -2Ax + 3, where A is a constant

When the polynomial P(x) = x3 + 3x2 -2Ax + 3, where A is a constant

When the polynomial P(x) = x3 + 3x2 -2Ax + 3, where A is a constant, is divided by x2 + 1 we get a remainder equal to -5x. Find A

Answer：Divide x3 + 3x2 -2Ax + 3 by (x2 + 1) to obtain a remainder = -x(1 + 2A)
-x(1 + 2A) = 5x : remainder given
-(1 + 2A) = 5 : polynomials are equal if they corresponding coefficient area equal.
A = -3 : Solve the above for A.