Question

定积分求解

rt,画?的这一步是怎么变过来的

Answer 1

解如下图所示

追问

感谢,明白了,另外麻烦帮忙看一下这道题

网页链接

Answer 2

这只有完全平方
(a-x)(x-y)
=-x^2+(a+y)x -ay
=-【 x-(a+y)x +[(a+y)/2]^2 】 +[(a+y)/2]^2 -ay
=- [ x - (a+y)/2]^2 + [(a-y)/2]^2
=[(a-y)/2]^2 - [ x - (a+y)/2]^2
and
dx = d( x- (a+y)/2)