2log25 X+logx 25=3求X=?.我在答案是这样写的“(log5 x -2)(logx 5 -1)=0"我想
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2log25 X+logx 25=3求X=?.我在答案是这样写的“(log5 x -2)(logx 5 -1)=0"我想问下化到
(log5 x)^2-3logx5+2=0是怎么化到“(log5 x -2)(logx 5 -1)=0"
(log5 x)^2-3logx5+2=0是怎么化到“(log5 x -2)(logx 5 -1)=0"
![2log25 X+logx 25=3求X=?.我在答案是这样写的“(log5 x -2)(logx 5 -1)=0](/uploads/image/z/17773136-8-6.jpg?t=2log25+X%2Blogx+25%3D3%E6%B1%82X%3D%3F.%E6%88%91%E5%9C%A8%E7%AD%94%E6%A1%88%E6%98%AF%E8%BF%99%E6%A0%B7%E5%86%99%E7%9A%84%E2%80%9C%EF%BC%88log5+x+-2%29%28logx+5+-1%29%3D0%22%E6%88%91%E6%83%B3)
错误的,换成常用对数得:
2log25 X+logx 25=3
2lgx/lg25+lg25/lgx=3
2(lgx)^2+(lg25)^2=3lg25lgx
2(lgx)^2-3lg25lgx+(lg25)^2=0
用十字相乘法
2 -1
1 -1
(2lgx-lg25)(lgx-lg25)=0
2lgx-lg25=0,lgx-lg25=0
lgx=1/2lg25,lgx=lg25
x=5,x=25
2log25 X+logx 25=3
2lgx/lg25+lg25/lgx=3
2(lgx)^2+(lg25)^2=3lg25lgx
2(lgx)^2-3lg25lgx+(lg25)^2=0
用十字相乘法
2 -1
1 -1
(2lgx-lg25)(lgx-lg25)=0
2lgx-lg25=0,lgx-lg25=0
lgx=1/2lg25,lgx=lg25
x=5,x=25
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