Question

因式分解（x+y)的平方加9(x-y)减6(x的平方减y的平方）

Answer 1

(x+y)^2+9(x-y)^2-6(x^2-y^2)

=(x+y)^2-6(x^2-y^2)+9(x-y)^2

=(x+y)^2-6(x-y)(x+y)+9(x-y)^2

=[(x+y)-3(x-y)]^2

=(x+y-3x+3y)^2

=(4y-2x)^2

=(2x-4y)^2

=4(x-2y)^2