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Math Help - deriv inverse fn?

  1. #1
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    deriv inverse fn?

    Let f(x) = x^3+x. If h is the inverse function of f then h'(2)=
    a. 1/13
    b.1/4
    c. 1
    d.4
    e. 13
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  2. #2
    MHF Contributor Mathstud28's Avatar
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    Ok

    Quote Originally Posted by sandiego234 View Post
    Let f(x) = x^3+x. If h is the inverse function of f then h'(2)=
    a. 1/13
    b.1/4
    c. 1
    d.4
    e. 13
    here is my favorite way of doing it....we have y=x^3+x...now to get the inverse we switch and solve back for y...but what if we did this....we say = x=y^3+y...then we say \frac{dx}{dy}=3y^2+1...therfore \frac{dy}{dx}=\frac{1}{3y^2+1}...therefore...we would get \frac{1}{13}
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