设2004x^2=2005y^5=2006z^2,xyz>0,且满足(2004x^2+2005y^2+2006z^2)^

清亮泉岭2022-10-04 11:39:541条回答

设2004x^2=2005y^5=2006z^2,xyz>0,且满足(2004x^2+2005y^2+2006z^2)^1/3=2004^1/3+2005^3+2006^1/3,求1/x+1/y+1/z的值.

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海是不里 共回答了21个问题 | 采纳率90.5%
y=(2004/2005)^(1/3)x
z=(2004/2006)^(1/3)x
则(2004x^2+2005y^2+2006z^2)^(1/3)
=(2004x^2+2005(2004/2005)^(2/3)x^2+2006(2004/2006)^(2/3)x^2)^(1/3)
=(2004x^2+2005^(1/3)2004^(2/3)x^2+2006^(1/3)2004^(2/3)x^2)^(1/3)
=(2004^(2/3)x^2(2004^(1/3)+2005^(1/3)+2006^(1/3)))^(1/3)
=2004^(1/3)+2005^(1/3)+2006^(1/3)
所以2004^(1/3)x=2004^(1/3)+2005^(1/3)+2006^(1/3)
x=(2004^(1/3)+2005^(1/3)+2006^(1/3))/2004^(1/3)
而1/x+1/y+1/z=1/x+(2005/2004)^(1/3)(1/x)+(2006/2004)^(1/3)(1/x)
=1/x(1+(2005/2004)^(1/3)+(2006/2004)^(1/3))
=1/x(2004^(1/3)+2005^(1/3)+2006^(1/3))/2004^(1/3)
=(1/x)*x=1
所以1/x+1/y+1/z=1
1年前

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