Friday

October 24, 2014

October 24, 2014

Posted by **Rachal** on Tuesday, February 15, 2011 at 11:09pm.

log3(x+7)=2-log3(x-1)

Write the exact answer using base-10 logarithms.

- Math -
**Reiny**, Tuesday, February 15, 2011 at 11:21pmlog3(x+7)=2-log3(x-1)

log3(x+7) + log3(x-1) = 2

log3 [(x+7)/(x-1)] = 2

(x+7)(x-1) = 3^2

x^2 + 6x - 7 = 9

x^2 + 6x - 16 = 0

(x+8)(x-2) = 0

x = -8 or x = 2

but x=-8 would make log3(x+7) undefined, so

x = 2

( why would it ask to use base 10 logs ????)

**Answer this Question**

**Related Questions**

Math - Solve the logarithmic equation. Express your solutions in exact form only...

Calculus - Find the inverse of each relation: y = (0.5)^(x+2) and y = 3log base ...

Math - (I have two questions) 1. Solve for x without a calculator: log3(x^2)=...

calculus - 1) Solve for x in terms of k: log3(x) + log3(x+7) = k; 3 is the base ...

Pre-Cal - 1) Solve the equation exactly for x: log3 x - log3(x-3) = 2 I got 1 as...

Math- logarithms - Why is (log3 400)/2 equivalent to log3 20? Can you show me ...

math - Solve for x in the following equations. (4 marks) log3(x - 5) + log3(x + ...

math - Write as a single log of a single argument: log3 24 + log3 17 - log3 51

Precalculus - Please help me with these questions ASAP!! Suppose that f(x)=log3...

ALGEBRA 1 - Lesson 3 Assignment .Explain the differences between solving these ...