(x1-x2)+(x2-x1)/x1x2 = (x1-x2)(1- 1/x1x2)

问题描述:

(x1-x2)+(x2-x1)/x1x2 = (x1-x2)(1- 1/x1x2)
请问这是怎么变形的?

提取公因式(x1-x2)