求定积分:∫(0→1)x^2√(1-x)dx

2024-11-07 22:34:25
有2个网友回答
网友(1):

答:
设t=√(1-x),t^2=1-x,x=1-t^2
x=0,t=1
x=1,t=0
原式
=(1→0) ∫[(1-t^2)^2/t]d(1-t^2)
=(0→1) 2∫[(1-2t^2+t^4)/t] dt
=(0→1) 2∫(1-2t^2+t^4)dt
=(0→1) 2[t-(2/3)t^3+(1/5)t^5]
=2*(1-2/3+1/5)-0
=12/5-4/3
=16/15

网友(2):

x^2/√(1-x)=[-2x^2(1-x)^(1/2)]'+4x(1-x)^(1/2)
=[-2x^2(1-x)^(1/2)]'+[-8x(1-x)^(3/2)/3]'+8(1-x)^(3/2)/3
=[-2x^2(1-x)^(1/2)-8x(1-x)^(3/2)/3]'+[-16(1-x)^(5/2)/15]'
=[-2x^2(1-x)^(1/2)-8x(1-x)^(3/2)/3-16(1-x)^(5/2)/15]'
上限1,所有项为0;对于下限0,只有最后一项不是0.
所以=16/15