00:01
In this problem, we're given the function f of x equals x to the two thirds.
00:04
We're given the graph of f of x, which i've sketched in blue, and the graph of f inverse of x, which i've sketched in green, and we're asked to find a formula for f inverse of x.
00:14
So to do that, we start with our formula for f of x, and then we need to solve for x.
00:20
So we want to get x equals instead of y equals, and then we just swap x and y.
00:27
So let's start by moving this exponent to the other side.
00:32
Let's raise both sides to the third power.
00:36
So on the right -hand side, that's going to cancel out with the third root, or there's three in the exponent here.
00:43
So y -cubed is equal to x -squared.
00:47
Now we want to take a square root of both sides.
00:51
So on the left -hand side, we have the square root of y -cubed is equal to the square root of x squared, and the square root of x squared is equal to the absolute value of x.
01:01
So we talked about why this is true in the video for problem 20.
01:04
So if you want to review that, you should check out problem 20.
01:09
But in this case, we know that we're given x is bigger than or equal to zero.
01:17
So because x is bigger than or equal to zero, x is positive...