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(x-5)/(3x³+6x)÷[21/(x+2)-x+2]
=(x-5)/[3x(x+2)]÷[(25-x²)/(x+2)]
=
=(x-5)/[3x(x+2)]÷[(25-x²)/(x+2)]
=
更多追问追答
追问
等于多少?。?
追答
x²+5x-1=0
x(x+5)=1
(x-5)/(3x²+6x)÷[21/(x+2)-x+2]
=(x-5)/[3x(x+2)]÷[(25-x²)/(x+2)]
=-1/[3x(x+5)]
=-1/(3*1)
=-1/3
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