f(x) = 1/2(x+4)(x-2)

Question

change it into vertex and standard form.

Answer 1

f(x) = (x + 4)(x - 2) / 2

f(x) = (x² + 2x - 8) / 2

f(x) = x²/2 + x - 4                      standard form

 

f(x) = (1/2)(x² + 2x      ) - 8       start completion of the square

f(x) = (1/2)(x² + 2x + 1) - 8 - 1/2

f(x) = (1/2)(x + 1)² - 8.5            vertex form