1.x³-1=(x-1)(x²+x+1) 立方差公式2.2a^2+4ab+2b^2=2（a²+2ab+b²）=2（a+b）²3.(xy)²-1=（xy+1）（xy-1）4.（x-y)^2+4xy =x²-2xy+y²+4xy=x²+2xy+y²=(x+y)²5....