Posted by **Rebekah** on Monday, November 19, 2012 at 8:28pm.

how do you find x in 7-=log(x/10^-12)

- Precalc -
**Reiny**, Monday, November 19, 2012 at 9:20pm
I will assume that -= is a typo and should be just =

7 = log(x/10^-12)

7 = logx - log 10^-12

7 = logx - (-12)

7-12= logx

-5 = logx

x = 10^-5

- Precalc -
**Rebekah**, Monday, November 19, 2012 at 10:11pm
the thing is its / instead of - so I thought that I multiply each side by 10^-12 but im not sure

- Precalc -
**Steve**, Tuesday, November 20, 2012 at 12:22am
you cannot multiply by 10^12 because that is inside the log.

suppose you had 2 = √(x/4)

You can't multiply by 4, giving

8 = √x

because that would be trying to slide a value through the "walls" of the function calculation

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