mehran Posted January 21, 2010 Share Posted January 21, 2010 If [math] f(x) = x^3 + x + 2[/math] and [math]f(a) = 9[/math] then: Calculate [math]f^{-1}(-5)[/math] at "a". This is the question that i'm thinking of it but i can't solve it at all! Does anyone know that how i can get to the answer? Link to comment Share on other sites More sharing options...
Bignose Posted January 23, 2010 Share Posted January 23, 2010 Given a f(x), you can find the inverse (if one exists, there certainly doesn't HAVE to be an inverse) by setting y=f(x) and then solving just for x. For example: let [math]f(x) = x^2 +1[/math] Set [math]y = x^2 +1 [/math] Then solve for x in terms of y: [math]y -1 = x^2 [/math] [math]\sqrt{y - 1} = x [/math] Then once you've isolated x, this is the inverse function: [math]x = f^{-1}(y) = \sqrt{y-1}[/math] Link to comment Share on other sites More sharing options...
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