(x+2y)²-x²-2xy
问题描述：
(x+2y)²-x²-2xy
(a+b)²-4(a-b)²
x^3n+y^3n
x^6+24x^3+144
x²-y²-z²+2yz+x+y+z
m²+n+2m+2n+2mn+1
答
1.(x+2y)^2-x^2-2xy =(x+2y)^2-(x^2+2xy) =(x+2y)^2-x(x+2y) =(x+2y)[(x+2y)-x] =2y(x+2y) 2.(a+b)^2-4(a-b)^2 =[(a+b)-2(a-b)][(a+b)+2(a-b)] =(a+b-2a+2b)(a+b+2a-2b) =(-a+3b)(3a-b) =-(a-3b)(3a-b) 3.x^3n+y^3n ...