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Math Help - inverse function intersections

  1. #1
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    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=]
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  2. #2
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    Quote Originally Posted by ella85 View Post
    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 ....?
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