(10x-10y)(x-y)+5x(x-y)=(10x-10y+5x)(x-y)=(15x-10y)(x-y)=15x^2-25xy+10y^2那把（y-x)变成（x-y)行不行(y-x)=-(x-y)我算了不对哪里不对，请指正。(15x-10y)(x-y)=5(x-y)(3x-2y)。y-x=-(x-y)而不是y-x=x-y。把（y-x)变成（x-y)之后得5﹙x－2y﹚﹙x－y﹚你要考虑正负号的变化啊，你不能傻傻的前面是负号你变号之后还是负号，你要明白负负得正，原先5x前的负号要变成正号。10(x-y)²那要变他怎么算啊-10（y-x）10(x-y)²=10(x-y)(x-y)=(10x-10y)(x-y).-5x(y-x)=5x(x-y)........这里有正负号的转变，看仔细了然后两式提取公因式，就得(10x-10y+5x)(x-y)－10﹙y－x﹚﹙y－x﹚－5x﹙y－x﹚=麻烦你了哦10(x-y)²=10(x-y)(x-y)=10[-(y-x)][-(y-x)]=10(y-x)(y-x)，变形过程中有两个负号了，所以还是正号。