4b的平方-4-4ab+a的平方
=(4b²-4ab+a²)-4
=(2b-a)²-4
=(2b-a+2)(2b-a-2)
-x的3次方y(tǒng)的3次方+x的平方y(tǒng)的平方-4分之1xy
=-xy/4 (4x²y²-4xy+1)
=-xy/4 (2xy-1)²
(x+y)的平方+9(x-y)的平方-6(y-x) (x+y)
=(x+y)²+6(x-y)(x+y)+9(x-y)²
=[(x+y)+3(x-y)]²
=(4x-2y)²
=4(2x-y)²
a的平方+2ab-c的平方+b的平方
=(a²+2ab+b²)-c²
=(a+b)²-c²
=(a+b+c)(a+b-c)