(a-b)蚂让御(x-y)-(a+b)滑梁(y-x)
=(a-b)(x-y)+(a+b)(x-y)
=(x-y)闷岩(a-b+a+b)
=(x-y).2a
=2ax-2ay
ax-ay-bx+by-(ay-ax+by-bx)=2ax-2ay=2a(x-y)
先后再前
=(a-b)(x-y)+(a+b)(x-y)
=(x-y)(a-b+a+b)
=2a(x-y)
(a-b)(x-y) - (a+b)(y-x)
=(a-b)(x-y) + (a+b)(x-y)
=(a-b + a+b)(x-y)
=2a(x-y)