+130516 We have
f(x) = y = 7^x take the log of both sides
log y = log 7 ^x and we can write
log y = x log 7 divide both sides by log 7
log y / log 7 = x exchange x and y
log x / log 7 = y for y, write f-1(x)
f-1(x) = log x / log 7
Here's the graph of f(x) and its inverse
https://www.desmos.com/calculator/g3lyto49l0
It depends on which inverse you need.
An inverse "undoes" an operation. So for addition, it would be subtraction. 7x would then be -7x.
For multiplication, 7x would be (1/7x).
+130516 We have
f(x) = y = 7^x take the log of both sides
log y = log 7 ^x and we can write
log y = x log 7 divide both sides by log 7
log y / log 7 = x exchange x and y
log x / log 7 = y for y, write f-1(x)
f-1(x) = log x / log 7
Here's the graph of f(x) and its inverse
https://www.desmos.com/calculator/g3lyto49l0
