The first three steps in writing f(x) = 40x + 5x2 in vertex form are shown. write the function in standard form. f(x) = 5x2 + 40x factor a out of the first two terms. f(x) = 5(x2 + 8x) form a perfect square trinomial. = 16 f(x) = 5(x2 + 8x + 16) – 5(16) what is the function written in vertex form? f(x) = 5(x + 4) – 80 f(x) = 5(x + 8) – 80 f(x) = 5(x + 4)2 – 80 f(x) = 5(x + 8)2 – 80