Question

(x+2y)的平方*(x-2y)的平方=多少

（x+2y-1）*（x-2y+1）-（x-2y-1）²

Answer 1

(x+2y)的平方*(x-2y)的平方=x^4-8x^2y^2+16y^4
（x+2y-1）*（x-2y+1）-（x-2y-1）²=x^2-(2y-1)^2-x^2-(2y+1)^2+2x(2y+1)=-8y^2+4xy+2x-2

Answer 2

(x+2y)²*(x-2y)²=[(x+2y)(x-2y)]²=(x²-4y²)²=x^4-8x²y²+16y^4;
（x+2y-1）*（x-2y+1）-（x-2y-1）²
=x²-(2y-1)²-(x²+4y²+1-4xy-2x+4y)
=x²-4y²+4y-1-x²-4y²-1+4xy+2x-4y
=-8y²-x²+4xy+2x+4y-2.