# inverse function intersections

• Apr 2nd 2009, 08:56 PM
ella85
inverse function intersections
I am having trouble with this question and various other similar ones:

Find the intersection of the graph 2log10(x+3) + 4 and its inverse.

I know you find the point where it intersects the line y = x
so i can get 2log10(x+3) +4 = x
and then rearrange to the point where (x-4)/2 = log10 (x + 3)
and 10^((x-4)/2) = x+3
but i can never get x on its own as the subject.
any help would be greatly appreciated=]
• Apr 2nd 2009, 09:00 PM
mr fantastic
Quote:

Originally Posted by ella85
I am having trouble with this question and various other similar ones:

Find the intersection of the graph 2log10(x+3) + 4 and its inverse.

I know you find the point where it intersects the line y = x
so i can get 2log10(x+3) +4 = x
and then rearrange to the point where (x-4)/2 = log10 (x + 3)
and 10^((x-4)/2) = x+3
but i can never get x on its own as the subject.
any help would be greatly appreciated=]

An exact solution can be found only by using the Lambert W-function.

But is an exact solution is required ....?