Question

Tolong bantuannya beserta penjelasannya yaa. terima kasih.

Answer 1

F(x)=3^x-1
misal f(x)=y
y=3^x/3
3y=3^x
log 3y=log 3^x
log 3y=x.log 3
x=log 3y/log3
x=^3log 3y
sehingga invers f(x)= ^3log 3x
invers f(81)=^3log 3.81 =^3log 3^5
Jadi f^-1(81)=5