Given the exponential function A(x) = P(1 + r)x, what value for r will make the function a decay function?

Question

r = −2.1
r = 2.1
r = 0
r = 0.1

Answer 1

Think of the graphs of e^x and e^-x
e^-x is a decay function, since
e^-x = (1/e)^x

A decay function a^x must have 0<a<1.

so, you need
0 < 1+r < 1
-1 < r < 0

None of the choices qualifies. a^x is not a real function if a<0.

I suspect a typo.