Question x-g-x-

2.1 Nonlinear Functions - Exponential growth and decay functions
0:00
x gx
-1 25
0 1
1 1 25
2 1 625

For the exponential function g , the table shows four values of x and their corresponding values of gx. Which equation defines g ?

A.

gx=-25x

B.

gx=-125x

C.

gx=25x

D.

gx=125x

x g x - 1 25 0 1 1 1 25 2 1 625 For the

Hard-difficulty · SAT Math · Nonlinear Functions — Exponential growth and decay functions. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice D is correct. It's given that function g is exponential. Therefore, an equation defining g can be written in the form gx=abx, where a and b are constants. The table shows that when x = 0 , gx=1. Substituting 0 for x and 1 for gx in the equation gx=abx yields 1=ab0, which is equivalent to 1 = a . Substituting 1 for a in the equation gx=abx yields gx=bx. The table also shows that when x = 1 , gx=125. Substituting 1 for x and 1 25 for gx in the equation gx=bx yields 125=b1, which is equivalent to 1 25 = b . Substituting 1 25 for b in the equation gx=bx yields gx=125x.

Choice A is incorrect. For this function, g1 is equal to - 25 , not 1 25 .

Choice B is incorrect. For this function, g1 is equal to - 1 25 , not 1 25 .

Choice C is incorrect. For this function, g1 is equal to 25 , not 1 25 .