Which is an exponential decay function?

f(x)= 3/4(7/4)^x
f(x)= 2/3(4/5)^-x
f(x)=3/2(8/7)^-x
f(x)=1/3(-9/2)^x

Step-by-step explanation:

An exponential decay function is of the form:

, where .

Or , where

The coefficient 'a' can be any non-zero real number.

is an exponential decay function, because it meets our first definition.

, is not an exponential decay function.

, is an exponential decay function, because it meets our second definition.

is also NOT an exponential decay function.

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)