How does f (t) = 4^t change over the interval from t=7 to t=8?

a) f (t) decreases by 4

b) f (t) increases by a factor of 4

c) f (t) decreases by 4%

d) f (t) increases by 400%

F (7) = 4⁷

f (8) = 4⁸ = 4·4⁷ = 4 f (7)

So f (t) increases by a factor of 4 from t=7 to t=8.

It's not A because that implies f (8) = f (7) - 4

It's not C because that implies f (8) = f (7) - 0.04 f (7) = 0.96 f (7)

It's not D because that implies f (8) = f (7) + 4.00 f (7) = 5 f (7)

Final answer: B