What is x if log(x+10) -log (3x-8)= 2?

1 Answer
Mar 11, 2018

see a solution step below..

Explanation:

log(x + 10) - log(3x - 8) = 2

Recall the law of logarithm..

loga - logb = loga/logb

Hence;

log(x + 10)/log(3x - 8) = 2 -> "applying law of logarithm"

log[(x + 10)/(3x - 8)] = 2

For every log, there is a base, and it's default base is 10, since there was no actual base specified in the given question..

Therefore;

log_10 [(x + 10)/(3x - 8)] = 2

Recall again the law of logarithm..

log_a x = y rArr x = a^y

Hence;

(x + 10)/(3x - 8) = 10^2 -> "applying law of logarithm"

(x + 10)/(3x - 8) = 100

(x + 10)/(3x - 8) = 100/1

1(x + 10) = 100(3x - 8) -> "cross multiplying"

x + 10 = 300x - 800

300x - 800 = x + 10 -> "rearranging the equation"

300x - x = 10 + 800 ->"collecting like terms"

299x = 810

x = 810/299 -> "diving both sides by the coefficient of x"

x = 2.70