Help on a algebra question.

Just substitute in for 'x
 

-3 (-1)^3 + 2 (-1)^2 = -3(-1) + 2(1) = 3 + 2 = 5

 

-3(1/2)^3 + 2(1/2)^2 = -3(1/8) + 2 (1/4) = -3/8 + 2/4 = 1/8