求不定积分

2025-05-16 10:15:44
推荐回答(2个)
回答1:

x=3/4 时,t²=1 - 3/4=1/4,t=1/2;
x=1 时,t²=1 - 1=0,t=0。

回答2:

∫(3/4,1) dx/[∨(1-x)-1]
令1-x=t²
x=3/4时,t=1/2;x=1时,t=0
则x=1-t²
dx=-2tdt
所以原式=∫(1/2,0) -2tdt/(t-1)
=2∫(0,1/2) tdt/(t-1)
=2∫(0,1/2) [1+1/(t-1)]dt
=2(t+ln|t-1|) |(0,1/2)
=2(1/2 +ln(1/2)-0-ln1)
=2(1/2-ln2)
=1-2ln2

(此题运用到∫1/x dx=ln|x|+C,不要忘记绝对值)