Algebra: A Combined Approach (4th Edition)

$a^{2}$ + 9a + 20
( a + 5 ) ( a + 4 ) use the commutative and associative properties multiply (a)(a) +(a)(4) +( 5)(a) + (5)(4) FOIL method $a^{2}$ + 4a + 5a + 20 $a^{2}$ + 9a + 20