PDA

View Full Version : Solving Calculus Logs


claire3158
Jul 29, 2009, 03:47 PM
1. Log(2)5 +log(2)(X^2-1) - log(2) (X-1)



2. 3^log(3)5



3. 2log(10) root of X +3log(10) X^1/3



Solving for the indicated variable... solve this equation for A..


4.x/a + y/b + z/c=1

Unknown008
Jul 30, 2009, 10:10 AM
These problems cannot be solved! There isn't any equal sign. However, you may simplify them.

I'll not give you the answers, but will give you the properties of logs.

log\, a + log\, b = log\, ab

log\, a - log\, b = log\, \frac ab

log\, a^b = blog\,a

log_b\, a = \frac{log\,a}{log\,b}

If x = log\,y, then y = 10^x

If x = log_a\,y, then, y = a^x

For number four, once again, you cannot solve that. There are too many variables. However, you can make 'a' the subject of formula.

galactus
Jul 30, 2009, 03:13 PM
1. log_{2}(5) +log_{2}(x^{2}-1) - log_{2}(x-1)
\;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \;\ \uparrow
................Is this supposed to be an =?
If that - is supposed to be an =, then we can proceed as such by noting that the bases are all the same. That makes it easier.

log(5)+log(x^{2}-1)=log(x-1)

log(5(x^{2}-1))=log(x-1)

5(x^{2}-1)=x-1

5x^{2}-x-4=0

Solve the quadratic. Make sure to check both solutions by plugging them back into the equation. One may be extraneous.