The steps in writing f(x) = 18x + 3x2 in vertex form are shown, but a value is missing in the last step. Write the function in s
tandard form. f(x) = 3x2 + 18x Factor a out of the first two terms. f(x) = 3(x2 + 6x) Form a perfect square trinomial. f(x) = 3(x2 + 6x + 9) – 3(9) Write the trinomial as a binomial squared. f(x) = 3(x + ______)2 – 27 What is the missing value in the last step?
Complete the square
coefficient of the x term: 6
divide it in half: 3
square it: 3²
use 3² to complete the square:
y = 3(x²+6x + 3²) - 3·3²
= 3(x+3)² - 3·3²
= 3(x+3)² - 27
vertex (-3, -27)</span>
