Question

If f(1)=160 and f(n+1)=−2f(n), what is f(4)?
A. 640
B. -1280
C. 2560
D. -5120

Answer 1

f(1) = 160

f(2) = -2f(1) = -2(160) = -320

f(3) = -2f(2) = -2(-320) = 640

f(4) = -2f(3) = -2(640) = -1,280

The correct answer is B.

Answer 2

To find f(4), we can start by finding the value of f(2) and f(3) using the given equation. Using the equation f(n+1) = -2f(n), we can find f(2) = -320 and f(3) = 640. Finally, plugging in n=3 gives us f(4) = -1280.

Step-by-step explanation:

To find f(4), we can start by finding the value of f(2) and f(3) using the given equation. Since f(n+1) = -2f(n), we can find f(2) by plugging in n=1, which gives us f(2) = -2f(1) = -2*160 = -320. Similarly, we can find f(3) by plugging in n=2, which gives us f(3) = -2f(2) = -2*(-320) = 640. Finally, we can find f(4) by plugging in n=3, which gives us f(4) = -2f(3) = -2*640 = -1280.