计算：a²/a-b-a-b/b²；3x/x-5-2x/5-x.

计算：a²/a-b-a-b/b²；3x/x-5-2x/5-x.
计算：a²/a-b-a-b/b²；3x/x-5-2x/5-x.

计算：a²/a-b-a-b/b²；3x/x-5-2x/5-x.
第一题 是 a²/(a-b) - b²/(a-b) 吧
a²/(a-b) - b²/(a-b)
= (a²-b²)/(a-b)
= (a+b)(a-b)/(a-b)
= a+b
3x/(x-5) - 2x/(5-x)
=3x/(x-5) + 2x/(x-5)
= 5x / (x-5)