Let be given by and be given by

MATHEMATICS · Single correct · AP · AP Precalculus · Exponential and Logarithmic Functions · Exponential and Logarithmic Functions

Problem

Let f:R→(0,∞)f:\mathbb R\to(0,\infty) be given by f(x)=ekxf(x)=e^{kx} and g:(0,∞)→Rg:(0,\infty)\to\mathbb R be given by g(y)=ln⁡(py)g(y)=\ln(py), where k>0k>0 and p>0p>0. For which ordered pair (k,p)(k,p) does each function serve as the inverse of the other, that is, g∘f=IRg\circ f=I_{\mathbb R} and f∘g=I(0,∞)f\circ g=I_{(0,\infty)}? (a) (k=2,  p=1)(k=2,\;p=1) (b) (k=1,  p=1)(k=1,\;p=1) (c) (k=1,  p=e)(k=1,\;p=e) (d) (k=2,  p=12)(k=2,\;p=\dfrac12)

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