To get G^-1 all we need to do is flip the points around Example for (5,3) make it (3,5) Here are the points in inverse (3,5); (3,2); (4,6) To tell if a group of point can be a function we need to 1st look at the x values. If all the x values are different, then it is a function (the x's are not all different) If there are x values that are the same, they MUST have the same y value. look at the points (3,5) and (3,2) those have the same x but they go to different y values so it is not a function.
You can think about it like this. Can you go to more than 1 place at the EXACT same time? Obvious answer is no. Can you have multiple people go to the same room? Sure that is possible. Same with functions. An x value can ONLY go to 1 y value, and many different x values can go to the same y value.
90 is the rate of change because the hot air balloon descends 90 feet per minute. And 2,000 is the starting point because the hot air balloon started the descent at 2,000 feet.
