已知25^x=2000,8^y=2000,则1/x+1/y等于() A.2 B.1 C.0.5 D.1.5
问题描述:
已知25^x=2000,8^y=2000,则1/x+1/y等于() A.2 B.1 C.0.5 D.1.5
答
B
答
25^x=2000,x=log25 2000 1/x=log2000 25
8^y=2000 y=log8 2000 1/y=log200 8
1/x+1/y=log2000 25+log200 8
=log2000 (25*8)
=log2000 200
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