An exponential curve passes through and is decreasing as increases

MATHEMATICS · Single correct · A Level · Mathematics · Exponentials and logarithms · Exponentials and logarithms

Problem

An exponential curve passes through

(0,18)

and is decreasing as

x

increases. Which of the following functions could represent this curve? (a)

y = 18\,(0.5)^{x}

(b)

y = 18\,(1.5)^{x}

(c)

y = 18\,(0.5)^{-x}

(d)

y = 9\,(0.5)^{x}