g(x) = k^(fx+1)
g(a) = b
=>
b = k^(fa+1)
=>
log(b) = log(k^(fa+1)
=>
log(b) = (fa+1)*log(k)
=>
log(b)/log(k) = fa+1
=>
log(b)/log(k) - 1 = fa
=>
log(b)/log(k) - 1
------------------ = f
        a

g(x) = k^((log(b)/log(k) - 1)*x/a + 1)
=>
g(x) = k*k^((log(b)/log(k) - 1)*x/a)
=>
g(x) = k*(b/k)^(x/a)