Solve the logarithmic equation for x. log18(x − 5) + log18(x + 2) = 1 x =

Algebra
Tutor: None Selected Time limit: 1 Day

Solve the logarithmic equation for x.
log18(x − 5) + log18(x + 2) = 1

x = 

Jul 16th, 2015

Hi !

log18(x - 5) + log18(x + 2) = 1

With same bases we can write

log18[(x - 5)(x + 2)] = 1

Now we can write

log18[(x - 5)(x + 2)] = log18(18^1)

So

(x - 5)(x + 2) = 18^1

x^2 + 2x - 5x - 10 = 18

x^2 - 3x - 10 = 18

x^2 - 3x - 10 - 18 = 0

x^2 - 3x - 28 = 0

x^2 + 4x - 7x - 28 = 0

x(x + 4) - 7(x + 4) = 0

(x + 4)(x - 7) = 0

x = - 4    x = 7

Hence 

Hope you get it. Thanks :)
Jul 16th, 2015

Are you studying on the go? Check out our FREE app and post questions on the fly!
Download on the
App Store
...
Jul 16th, 2015
...
Jul 16th, 2015
Dec 8th, 2016
check_circle
Mark as Final Answer
check_circle
Unmark as Final Answer
check_circle
Final Answer

Secure Information

Content will be erased after question is completed.

check_circle
Final Answer