Friday

March 6, 2015

March 6, 2015

Posted by **marcus** on Wednesday, November 21, 2012 at 3:05am.

5 In x=10?

log(x+25)=1+ log(2x-7)?

- precalculus -
**Kay**, Wednesday, November 21, 2012 at 4:51amYou have to know the logarithm rules and definition

Definition: if log(base a)x=b then x=a^b

Rules-I am going to use base 10 but it applies for every base:

1) loga^r=rloga

2)log(a*b)=loga+logb

3)log(a/b)=loga-logb

4)change of base: loga=log(base b)a/log(baseb)10

So the first one I don't understand question.

Second: lnx=2 so x=e^2 (by definition)

Third: log(x+25)-log(2x-7)=1 so by using 3rd law: log[(x+25)/(2x-7)]=1 and then definition; 10^1= (x+25)/(2x-7) so cross multiplying; 10(2x-7)=x+25 so 20x-70=x+25 19x=95 x=5

Hope this helps

**Answer this Question**

**Related Questions**

math - Logarithm!!! Select all of the following that are true statements: (a) ...

Math Help Please - Which of the following expressions is equal to log (x sqrt-y...

Advanced Functions/ Precalculus Log - 1. Evaluate 4^(log base4 64) + 10^(log100...

Mathematics - Prove that log a, log ar, log ar^2 is an a.p. Is the following ...

Algebra 2 - how do not understand how to do this Log X + Lob (X-3) = 1 I know I ...

math(Please help) - 1) use the properties of logarithms to simplify the ...

math - write as a single logarithm: -2logbase3(1/x)+(1/3)logbase3(square root of...

Precalculus - PLEASE HELP ME WITH THESE QUESTION AS MUCH AS POSSIBLE!! Evaluate...

Trigonometry - This is a logs question If u=x/y^2, which expression is ...

Math/trig - Log radical b/ a^2 is equivalent to 1) 1/2 log b + 1/2 log a 2) l/2 ...