[f(x+h) - f(x) ] /h = [2(x+h)^2 + (x+h) - 1 - (2x^2 + x -1) ] / h =
= [ 2 (x^2 + 2xh + h^2) + x + h - 1 - 2x^2 - x + 1] / h =
= [2x^2 + 4xh + 2h^2 + x + h - 1 - 2x^2 - x + 1] / h =
= [4xh + 2h^2 + h] / h = 4x + 2h + 1
Answer: 4x + 2h + 1
Do you want the limit of that when h → 0? It is 4x + 2(0) + 1 = 4x + 0 + 1 = 4x + 1
