請問如何求出f(4)之值?

Sol
f(x)=10000e^(－kx)
f(2)=10000*e^(－2k)=100
e^(-2k)=1/100
f(4)=10000*e^(－4k)
=10000*[e^(－2k)]^2
=10000*(1/100)^2
=1

f(x)=ae^(-kx)
f(2)=10000e^(-2k)
100=10000e^(-2k)
k=In(0.01)/-2
f(4)=10000e^(2In(0.01))=1