4-5

We learned section 4-5 to complete the rest of chapter 4 before we go back to trig. It was all about finding inverses of a problem. It was very simple and easy because all you have to do is switch the x’s and y’s in a problem and then solve for y. There are very few steps and it is pretty simple. BEFORE you solve the problem, you need to graph the equation on a coordinate plane and use the horizontal line test.

The horizontal line test is where you draw horizontal lines across a graph. If it does NOT touch more than one point, then it is an inverse. According to the book, if it does not pass this test, then an inverse does not exist. We did learn though that in college, we will be told something different. Also, when you find the inverse, you put an exponent of -1 after the y to show that it is an inverse.

Once you passed the horizontal line test, you can get to working the problem:

Example:

Find the inverse for y = x -9
You graph this equation, and do the horizontal line test, and it does pass.
1. Switch the x and y. x= y-9
2. Solve for y. y = x + 9
3. Y^-1 = x + 9