Logarithms
posted by leo on .
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.......
:)

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)] 
thank you