Question

Which expression represents 36x^2-100y^2 factored completely

Answer 1

36 and 100 are both perfect squares
the factorization of x^2-y^2 is (x+y)(x-y)
substitute x^2 with 36x^2 and y^2 with 100y^2:
36x^2-100y^2=
(6x+10y)(6x-10y) or 
4(3x+5y)(3x-5y)