Which of the following equations represents exponential decay?

y=−3x+5

y=3(0.8)x

y=−3x−5

y=0.8(3)x

y=3(0.8)x

Step-by-step explanation:

An exponential function is a function of the form;

The explanatory variable x is the exponent, a is the initial value and b the base of the exponential function.

The function is said to be an exponential decay function if the base is between 0 and 1;

0<b<1

Therefore, y=3(0.8)^x is the required function. The values of y become smaller as x increases.

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50