Today’s topics are exponential growth functions and exponential decay functions.

An exponential growth function can be written as the following:

y = C(1+r)^t

where t represents time, r is called growth rate (r > 0), 1+r is called growth factor, C is in the initial value.

A good example to help understand the exponential growth function is the simple bank annual interest. r will be the annual interest rate, t represents number of year, C is the initial deposit, and y is the total amount after t years.

Similarly, an exponential decay function can be written as the following:

y = C(1-r)^t

where t represents time, r is called decay rate (1 > r > 0), 1-r is called decay factor, C is the initial value.

A good example would be car losing value as 10% per year.

This lesson finishes the chapter 8. Next time we will do a review of what we have learned in the first 6 lessons, to get ready for the mid term exam two weeks from now, on 11/6.

Here is the homework:

http://blog.newtonchineseschool.org/wangweidong/files/2011/10/Math7_Fall_HW_L6.pdf