Question

解方程：(x-5)(x^2-x+1)-x(2^2-6x)=19

Answer 1

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