Maths log
2012-10-13 1:47 am
Solve the equation (log base 5 X-log base x 25=1). ( Give the answers correct to 3 sig. figures if necessary.)
回答 (1)
2012-10-13 2:09 am
✔ 最佳答案
Solve the equation (log base 5 x－log base x 25=1). ( Give theanswers correct to3 sig. figures if necessary.)
Sol
log5_x－log25_x=1
logx/log5－log25/logx=1
Set y=logx/log5
y－2/y=1
y^2－2=y
y^2－y－2=0
(y－2)(y+1)=0
y=2 or y=－1
(1) y=2
2=logx/log5
x=25
(2) y=－1
－1=logx/log5
x=1/5=0.2
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