Which ordered pairs lie on the graph of the exponential equation?

a) f(x)=2(3)^2x
(0,2)
(1,20)
(-1, 2/9)
(2, 150)

b) f(x)=240(0.25)^x
(0, 240)
(1, 50)
(2, 15)
(-1, 960)

c) f(x)=5(1/2)^x
(0, 0)
(2, 5/4)
(-1, 10)
(-2, 20)