Answer:
Explanation:
Given
y = x^2 + 10x + 21
Complete the square
y = x^2 + 10x + 21 Put brackets around the first 2 terms
y = (x^2 + 10x) + 21 Take 1/2(10) and square it. Add inside the brackets.
y = (x^2 + 10x + 5^2) + 21 Subtract 5^2 after 21
y = (x^2 + 10x + 25) + 21 - 25 Make (x^2 + 10x + 25) into a perfect square.
y = (x + 5)^2 - 4
Answer: (x + 5)^2 - 4