8. Suppose an investment of $5,000 doubles every 12 years. How much is the investment worth after 36 years? After 48 years? Write and solve an exponential equation.

It's a doubling time question, so the formula will have the form of y = a (2) ^ (x/t). Y is the present amount; a is the initial amount; x is the number of year; t is the period of doubling time.

So now you just plug in values:

y = 5000 (2) ^ (36/12)

y = 5000 (2^3)

y = 5000 (8)

y = 40 000

And it's the same for the second part (just with 48 instead of 36):

y = 5000 (2) ^ (48/12)

y = 5000 (2^4)

y = 5000 (16)

y = 80 000