Plug in (4,64) into each answer choice.
A) 4(2)^x
64 =4(2)^4
64 = 4(16)
64 = 64
Answer choice A is correct.
B) f(x) = 2(4)^x
64 = 2(4)^4
64 = 2(256)
64 ≠ 512
Answer choice B is incorrect.
C) f(x) = 4(2)^{-x}
64 = 4(2)^{-4}
64 = 4(-0.0625)
64 ≠ 0.25
Answer choice C is incorrect.
D) f(x) = 2(4)^{-x}
64 = 2(4)^{-4}
64 = 2(0.00390625)
64 ≠ 0.0078125
Answer choice D is incorrect.
Your answer is B) f(x)=2(4)^x