15、分解因式;x(x-y)-y(y-x) x(x-y)-y(y-x) =x(x-y)+y(x-y)=(x+y)(x-y)16、小雨同学在计算34.3乘以17.1加上82.5乘以17.1减去26.8乘以17.1加上10乘以17.1 .34.3×17.1+82.5×17.1-26.8×17.1+10×17.1=(34.3+82.5-26....