(x+(1/x)-2)³展开式中常数项是

(x+(1/x)-2)³展开式中常数项是
(x+(1/x)-2)³展开式中常数项是

(x+(1/x)-2)³展开式中常数项是
-20

(x+(1/x)-2)³
=[(x²-2x+1)/x ]³
=[(x-1)²/x]³
=[(x-1)²]³/x³
=[(x-1)³]²/x³
=(x³-3x²+3x-1)²/x³
=(1-3/x+3/x...

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(x+(1/x)-2)³
=[(x²-2x+1)/x ]³
=[(x-1)²/x]³
=[(x-1)²]³/x³
=[(x-1)³]²/x³
=(x³-3x²+3x-1)²/x³
=(1-3/x+3/x²-1/x³)(x³-3x²+3x-1)
由此可得常数项为
1*（-1）=-1
-3/x * 3x = -9
3/x² * (-3x²)=-9
-1/x³ * x³ = -1
-1 + -9 + -9 + -1 =-20

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