Choose among these options the one that results in a graph that shows exponential decay. a. f(x) = 0.6(2)x b. f(x) = 3(0.7)x c. f(x) = 0.4(1.6)x d. f(x) = 20(3)x

 [B]:  " f(x) = 3(0.7)ˣ " .

x  | y         
0 | 3
1  | 2.1
2 | 1.48

When, "x" [which is the exponent] increases" ; the resulting value; "y" on a graph, DECREASES;  hence; "exponential decay". 

Consider Choice [A]:  " f(x) = 0.6(2)ˣ " .

x  | y         
0 | 0.6
1  | 1.2
2 | 2.4 ;

When "x" [the exponent] increases, the resulting value; "y" (on a graph); INCREASING;  indicating 'exponential growth' ; NOT 'exponential decay' .

Consider Choice [C]:  "f(x) = 0.4(1.6)ˣ " .

x  | y         
0 | 0.4
1  | 0.64
2 | 1.024

When "x" [the exponent] increases, the resulting value; "y" (on a graph); INCREASING;  indicating 'exponential growth' ; NOT 'exponential decay' .

→ As such, Choice: [C]:  is incorrect.

Consider Choice [D]:  " f(x) = 20 * (3)ˣ  " ; 

x  | y         
0 | 20
1  | 60
2 | 180 ;


When "x" [the exponent] increases, the resulting value; "y" (on a graph); INCREASING;  indicating 'exponential growth' ; NOT 'exponential decay;.

→ As such, "Choice [D]" is incorrect.

Chope that

The answer would be 484