# math(log)

find x if

a) 1/81=3^2x-1

b)log2x+ 3/log2x = 4

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1. since 81 = 3^4, we have

3^-4 = 3^(2x-1)
-4 = 2x-1
x = -3/2

logx + 3/logx = 4
log^2(x) - 4logx + 3 = 0
(logx-1)(logx-3) = 0
logx = 1,3
x = 2,8
check:
1+3/1 = 4 yes
3+3/3 = 4 yes

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posted by Steve
2. star

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posted by fizz

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