Which of the following options results in a graph that shows exponential growth? f(x) = 0.4(3)x f(x) = 3(0.5)x f(x) = 0.8(0.9)x f(x) = 0.9(5)−x

It's important that you use the correct symbol to indicate exponentiation.

f(x) = 0.4(3)x f(x) = 3(0.5)x f(x) = 0.8(0.9)x f(x) = 0.9(5)−x   should be written as:

f(x) = 0.4(3)^x f(x) = 3(0.5)^x f(x) = 0.8(0.9)^x f(x) = 0.9(5)−x.  

Please double-check that last problem, as I am unsure of whether you meant 0.9^5 or (0.9)(5).

f(x) = 0.4(3)^x is definitely an exponential function.

Please try again.  Do those problems that you can do an ask questions about the others.

4x 20 is 80 but if ther machine is broken then there is none you have to redo the test