Question

P(x)= x^3+4x^2-8x-6 a= -2

Answer 1

Unfortunately, you haven't shared the instructions for this problem.  My guess is that you are to evaluate P(x)= x^3+4x^2-8x-6 for x = a = -2.

If that's the case, then

P(-2) = (-2)^3 + 4(-2)^2 - 8(-2) - 6.  This simplifies to:

         =  -8      +  16 + 16 - 6  = 18 (answer)