Posted by **leo** on Saturday, March 22, 2008 at 5:14pm.

Hi,

Can anyone tell me if the following are correct please:-

If x = 10y (where x > 0), then log10 x = y

if a and b are positive numbers, then,

2 log 10 a / b = 2log 10 a - 2 log 10 b

and lastly

if a and b are positive numbers, then,

log 10 ( a+b ) = 10 log 10 a + log 10 b

Thanks.......

:-)

- Logarithms -
**Reiny**, Saturday, March 22, 2008 at 5:33pm
You have a typo in

"If x = 10y (where x > 0), then log10 x = y "

should say: If x = 10^y (where x > 0), then log10 x = y

the second one is right

the third one is wrong

log (a+b) cannot be split up

your answer of 10 log 10 a + log 10 b would be

log_{10}[(a^10)(b)]

- Logarithms -
**leo**, Saturday, March 22, 2008 at 5:42pm
thank you

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