Question

Question 3

The expression x^2- 8x + 21 can be written in the form (x - a)^2+ b for all values of x
(a) Find the value of a and the value of b.

Answer 1

a = 4, b = 5

Explanation:

x² - 8x + 21

Using the method of completing the square

add/subtract ( half the coefficient of the x- term )² to x² - 8x

x² + 2(- 4)x + 16 - 16 + 21

= (x - 4)² + 5 ← in the form (x - a)² + b

with a = 4 and b = 5