in exponential decay, the value under the exponent must be less than 1 and more than 0
but wait, we have exponents that are negative values, that's interesting
it's a trick, we need to convert it to form [tex]f(x)=ab^x[/tex]
remember that [tex](\frac{a}{b})^{-1}=\frac{b}{a}[/tex]
also that [tex]a^{bc}=(a^b)^c[/tex]
therefor [tex]f(x)=a(\frac{b}{c})^{-x}=a((\frac{b}{c})^{-1})^x=a(\frac{c}{b})[/tex]
so those ones that have the -x exponent, we need to flip the fraction
first one is 7/4, that is more than1
2nd one has a negative exponent so it becomes (3/4)(5/4)^x and 5/4 is greater than 1
3rd one has negative exponent so it becomes (3/2)(7/8)^x and 7/8 is less than 1
4th one is 9/2 and that's more than 1
3rd one is answer or [tex]f(x)=(\frac{3}{2})(\frac{8}{7})^{-x}[/tex] is an exponential decay function
