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  Discussion about math, puzzles, games and fun.   Useful symbols: √ ∞ ≠ ≤ ≥ ≈ ⇒ ∈ Δ θ ∴ ∑ ∫ π -

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Topic review (newest first)

mathsyperson
2005-10-25 20:57:23

Use the identity a log b = log (b^a).

1) ln (x+1) = 2 ln (x+1)
ln (x+1) = ln (x+1)
x+1 = x+2x+1
2x = 0
x = 0

2) log (7x-12) = 2 log x
log (7x-12) = log (x)
7x-12 = x
x-7x+12 = 0
(x-4)(x-3) = 0
x = 3 or 4

Bboy PhysicX
2005-10-25 20:39:44

Hi! can you teach me how to do this thing?
I'm really confused... so please~~
THANK YOU~

Solve:

ln (x^2 + 1) = 2 ln (x + 1)

and

log (7x - 12) = 2 log x

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