Answer:
a = - 2, b = 5
Explanation:
expand the right side using FOIL and compare the coefficients of like terms on both sides.
(x + a)² + b
= x² + 2ax + a² + b
compare terms with x² - 4x + 9
coefficients of x- term
- 2a = 4 ( divide both sides by - 2 )
a = - 2
compare constant terms
a² + b = 9
(- 2)² + b = 9
4 + b = 9 ( subtract 4 from both sides )
b = 5