方程是不是：(x-5)(x^2-x+1)-x(x^2-6x)=19
(x-5)(x^2-x+1)-x^2(x-6)=19
(x-5)(x^2-x+1)-x^2[(x-5)-1]=19
(x-5)(x^2-x+1-x^2)+x^2=19
(x-5)(-x+1)+x^2=19
-x^2+6x-5+x^2=19
6x=24
x=4
或者全部展开：
x^3-x^2+x-5x^2+5x-5-x^3+6x^2=19
立方项和平方项全部消去：6x=24
x=4