Saturday

November 22, 2014

November 22, 2014

Posted by **Anonymous** on Monday, August 25, 2008 at 6:25pm.

I know how do the example in my book but I don't know what I'm doing wrong here.

log4 x + log4(x-2)=log4(15)

log4 [x + log4(x-2)]=log4(15)

(x^2 + x)=4

x^2 + x-4=0

- Logarithms -
**Reiny**, Monday, August 25, 2008 at 6:43pmI see two major errors

1. from log A + log B = log (A x B)

your second line should have been

log4 [x(x-2)]=log4(15)

then in your third line

the right side should have been 15, not 4

so

x(x-2) = 15

x^2 - 2x - 15 = 0

(x-5)(x+2) = 0

x = 5 or x = -2, but x+-2 does not work since you cannot take the log of a negative

so x=5

- Logarithms (CORRECTION) -
**Reiny**, Monday, August 25, 2008 at 6:49pmshould have been

x-5)(x+3) = 0

x = 5 or x = -3, but x=-3 does not work since you cannot take the log of a negative

so x =l 5 is still the only solution

- Logarithms (CORRECTION) -

**Answer this Question**

**Related Questions**

Algebra 2 - Simplify: 1. 2log10^5+log10^4 2. 2log3^6-log3^4 3. log4^40-log4^5 4...

Algebra II - Solve, round to four decimal places if necessary: log4(x-9)=2 ...

Math(Please check) - solve for x: log4 X - log4 2 = 2 log(2x) = 2 Now what do I ...

Math - solve for x: log4 X - log4 2 = 2 log(2x) = 2 Now what do I do?

math - Solve the equation algebraically. Round the result to three decimal ...

Math - Evaluate the expression without using a calculator: log4(2)= ____? Use a ...

math - log4(2x+4)-3 =log4 3

Algebra 2 - log4 (x-2) - log4 (x+1) = 1

Trig/Pre-Calc - Could someone please help me on this problem. I'm really ...

Math Algebra 2 - #4. Express the logarithm in terms of log2M and log2N: log2 1/...