Solve f(x)=2 what point on graph of f g(x)=3 what point on the graph of g f(x)=g(x) do the graph of f and g intersect if so where f(x)=log 3 (x+5) and g(x)=log 3 (x-1).Please help.

1 Answer

beckden's profile pic

beckden | High School Teacher | (Level 1) Educator

Posted on

We are going to be using the definiton of logarithm that

`log_b(a)=c hArr b^c=a`


`f(x)=2` when


Raising 3 to both sides gives us


And by the definition of logarithm

` x+5=9`


Solving for x we get

`x=4` , and we should check that answer to make sure we do not have an extraneous solution.

`f(4)=log_3(4+5)=log_3(9) = log_3(3^2)=2` so our answer checks.



when does g(x)=3 so we have to solve




So `x = 28` we should check,



Now we want to find when `f(x)=g(x)`


Raise 3 to both sides to get


`x+5 = x - 1`

Subtracting x from both sides gives us

5=-1 which is never true, so there is no place where `f(x)=g(x)` .

To recap, `f(x)=2` when `x=4, g(x)=3` when `x=28` , and there is no solution to `f(x)=g(x)`