Question

因式分解：25(x+y)^2-60(x^2-y^2)+36,

Answer 1

25(x+y)^2-60(x^2-y^2)+36(x-y)^2=[5(x+y)^]2-60(x-y)(x+y)+[6(x-y)]2=[5(x+y)-6(x-y)]2=(11y-x)^2