求积分,请详细解答,谢谢!
1个回答
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1.
∫[1/e:e]|lnx|dx
=∫[1/e:1](-lnx)dx +∫[1:e]lnxdx
=x(1-lnx)|[1/e:1]+x(lnx -1)|[1:搏让e]
=1·(1-ln1)-(1/e)·[1-ln(1/e)] +e·(lne -1) -1·(ln1 -1)
=1 - 2/e +0 +1
=2(e-1)/e
2.
∫[-2:2][(|x|+x)e^(-|x|)]dx
=∫[-2:0][(|x|+x)e^(-|x|)]dx+∫[0:2][(|x|+x)e^(-|x|)]dx
=∫[-2:0][(-x+x)e^(-|x|)]dx+2∫[0:2]xe^(-x)dx
=0-2∫[0:2]xd[e^(-x)]
=-2xe^(-x)|[0:2]-2∫[0:2]e^(-x)d(-x)
=-2(2·e⁻²-0·e⁰) -2e^(-x)|[0:2]
=-4·e⁻戚绝²基仔局 -2(e⁻²-e⁰)
=2-6·e⁻²
=2(e²-3)/e²
∫[1/e:e]|lnx|dx
=∫[1/e:1](-lnx)dx +∫[1:e]lnxdx
=x(1-lnx)|[1/e:1]+x(lnx -1)|[1:搏让e]
=1·(1-ln1)-(1/e)·[1-ln(1/e)] +e·(lne -1) -1·(ln1 -1)
=1 - 2/e +0 +1
=2(e-1)/e
2.
∫[-2:2][(|x|+x)e^(-|x|)]dx
=∫[-2:0][(|x|+x)e^(-|x|)]dx+∫[0:2][(|x|+x)e^(-|x|)]dx
=∫[-2:0][(-x+x)e^(-|x|)]dx+2∫[0:2]xe^(-x)dx
=0-2∫[0:2]xd[e^(-x)]
=-2xe^(-x)|[0:2]-2∫[0:2]e^(-x)d(-x)
=-2(2·e⁻²-0·e⁰) -2e^(-x)|[0:2]
=-4·e⁻戚绝²基仔局 -2(e⁻²-e⁰)
=2-6·e⁻²
=2(e²-3)/e²
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