How do you factor the trinomial #3(a + b)^2 - 18(a + b) - 216#?
1 Answer
Mar 30, 2018
Explanation:
#"using the substitution "x=a+b#
#rArr3(a+b)^2-18(a+b)-216#
#=3x^2-18x-216#
#"take out a "color(blue)"common factor "3#
#=3(x^2-6x-72)#
#"the factors of - 72 which sum to - 6 are - 12 and + 6"#
#=3(x-12)(x+6)#
#"change x back to "a+b#
#=3(a+b-12)(a+b+6)#
