解ï¼
14ãéB
1/m+1/n=1/(m+n)
(m+n)/(mn)=1/(m+n)
mn=(m+n)²
æ以n/m+m/n=(n²+m²)/mn=[(m+n)²-2mn]/mn=ï¼m+nï¼²/(mn)-2
=1-2=-1
15ãå¡«2001
[(x-2)³-(x-1)²+1]/(x-2)
= [(x-2)³-((x-1)²-1)]/(x-2)
= [(x-2)³-x(x-2)]/(x-2)
= (x-2)²-x
= x²-4x+4-x
= x²-5x-1997+2001
= 2001
14ãéB
1/m+1/n=1/(m+n)
(m+n)/(mn)=1/(m+n)
mn=(m+n)²
æ以n/m+m/n=(n²+m²)/mn=[(m+n)²-2mn]/mn=ï¼m+nï¼²/(mn)-2
=1-2=-1
15ãå¡«2001
[(x-2)³-(x-1)²+1]/(x-2)
= [(x-2)³-((x-1)²-1)]/(x-2)
= [(x-2)³-x(x-2)]/(x-2)
= (x-2)²-x
= x²-4x+4-x
= x²-5x-1997+2001
= 2001
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