Find a, given that 5 is the remainder when x to the fourth power -
2x cubed + ax squared - x - 1 is divided by x + 2?
let f(x) = x^4 - x^3 + ax^2 - x - 1
when divided by x+2 leaves a remainder of 5
f(-2) = 5
16 - (-8) + 4a - (-2) - 1 = 5
4a = -20
a = -5