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**Bboy PhysicX****Guest**

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

**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

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

1) ln (x²+1) = 2 ln (x+1)

ln (x²+1) = ln (x+1)²

x²+1 = x²+2x+1

2x = 0

x = 0

2) log (7x-12) = 2 log x

log (7x-12) = log (x²)

7x-12 = x²

x²-7x+12 = 0

(x-4)(x-3) = 0

x = 3 or 4

Why did the vector cross the road?

It wanted to be normal.

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