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Thread: Finding values for a function with horizontal asymptote

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    Finding values for a function with horizontal asymptote

    Find values of a,b, and c for exponential function f(x) = cb^-x + a. Given that horizontal asymptote is y=72. Y-intercept is 425 and point P(1,248.5) lies on the graph.

    Can anyone explain this step-by-step?
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    Quote Originally Posted by mwok View Post
    Find values of a,b, and c for exponential function f(x) = cb^-x + a. Given that horizontal asymptote is y=72. Y-intercept is 425 and point P(1,248.5) lies on the graph.

    Can anyone explain this step-by-step?
    as x gets large, $\displaystyle cb^{-x}$ gets very small ... $\displaystyle a = 72$

    y-intercept at $\displaystyle x = 0$ ... $\displaystyle cb^0 + 72 = 425$ ... $\displaystyle c = 353$

    $\displaystyle x = 1$ ... $\displaystyle 248.5 = 353 \cdot b^{-1} + 72$

    you solve for $\displaystyle b$.
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