Find the inverse function

Question

f(x)=10^3x I found y=1/3 log x

f(x)= log2(4x) I found y=2/4^x

Am I right ?

Answer 1

#1 ok
#2 nope
x = log_2(4y)
2^x = 4y
y = 2^x/4 = 2^(x-2)

or,
x = log_2(4y)
x = log_2(4) + log_2(y)
x = 2 + log_2(y)
x-2 = log_2(y)
y = 2^(x-2)

If y = 2/4^x is the inverse, then f(x) = log_4(2/y)