(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)變成（x-y)行不行(y-x)=-(x-y)我算了不對哪里不對，請指正。(15x-10y)(x-y)=5(x-y)(3x-2y)。y-x=-(x-y)而不是y-x=x-y。把（y-x)變成（x-y)之后得5﹙x－2y﹚﹙x－y﹚你要考慮正負號的變化啊，你不能傻傻的前面是負號你變號之后還是負號，你要明白負負得正，原先5x前的負號要變成正號。10(x-y)²那要變他怎么算啊-10（y-x）10(x-y)²=10(x-y)(x-y)=(10x-10y)(x-y).-5x(y-x)=5x(x-y)........這里有正負號的轉(zhuǎn)變，看仔細了然后兩式提取公因式，就得(10x-10y+5x)(x-y)－10﹙y－x﹚﹙y－x﹚－5x﹙y－x﹚=麻煩你了哦10(x-y)²=10(x-y)(x-y)=10[-(y-x)][-(y-x)]=10(y-x)(y-x)，變形過程中有兩個負號了，所以還是正號。