Question

4(x+y)²-20（x+y）+25

Answer 1

4(x+y)²-20（x+y）+25

=[2(x+y)-5]^2

=(2x+2y-5)^2

（x²+4y²）-（-4xy+1）

=(x^2+4y^2+4xy)-1

=(x+2y)^2-1

=(x+2y+1)(x+2y-1)