How do you factor the trinomial #x^2-8xy-9y^2#?
1 Answer
Dec 26, 2015
Factor by grouping to find:
#x^2-8xy-9y^2=(x-9y)(x+y)#
Explanation:
You can split the middle term and factor by grouping as follows:
#x^2-8xy-9y^2#
#=x^2+xy-9xy-9y^2#
#=(x^2+xy)-(9xy+9y^2)#
#=x(x+y)-9y(x+y)#
#=(x-9y)(x+y)#
The choice of split comes from finding a pair of factors of
