omckyyo的部落格

標題:

• Maths questions_1
• 我想問唯舞獨尊好玩D定係勁舞團好玩D---
• find e,f,g,h@1@

此文章來自奇摩知識+如有不便請留言告知

Logarithmic Question

發問:

If 2^x = 5^y = 10^z, then A. z = xy B. z = x + y C. z = (x+y)/(xy) D. z = (xy)/(x+y) step + ans

最佳解答:

2x= 5y = 10z xlog2 = ylog5 = z x = z/log2 y = z/log5 1/x+1/y =(1/z)(log2+log5) =1/z 1/z= (x+y)/xy z = xy/(x+y) Therefore,the answer is D

其他解答:

選得好!!! copy cat 的回答不可以做最佳ge !!!|||||2^x = 5^y = 10^z x log2 = y log5 = z(log2 + log5) x log2 = y log5 x/y = log5/log2 y log5 = z(log2 + log5) z/(y-z) = log5/log2 x/y = z/(y-z) xy-xz = yz z(y+x) = xy z = xy/(x+y) The answer is D.