2(y-x)的平方-7(x-y)+6(x-y)-3(y-x)的平方

2(y-x)的平方-7(x-y)+6(x-y)-3(y-x)的平方

2(y-x)²;-7(x-y)+6(x-y)-3(y-x)²;
=-(y-x)²;-(x-y)
=-(x-y)²;-(x-y)
=-(x-y)[(x-y)+1]
=(y-x)(x-y+1)