Many students (and even teachers) have no idea that a polynomial solver and system of equations solver is already installed in all TI-84 Plus series calculators. Because the interface can be slightly confusing to navigate, I still recommend creating a quadratic formula program to solve 2nd order polynomials, but for anything higher, the PlySmlt2 app is the way to go.
Getting to the App
To find the app, all you have to do is press the apps button and scroll down to PlySmlt2. Let’s start by learning how to work the polynomial root finder tool which solves all x-intercepts for a polynomial function.
Polynomial Root Solver
The first screen you encounter contains all parameter options. To test the program, we are going to solve for a 3rd order polynomial (x3). We will be solving for real numbers, and won’t be using any trigonometric functions so the radian/degree doesn’t matter. Therefore, we can leave the remaining five options as default. For our sample function let’s try to solve the polynomial x3 – 3x2 – 10x + 24 = 0. Make sure to choose the correct operator (+/-) before each value.
After that, just press graph to solve! It should provide you with the answers x = -3, 2, and 4. To confirm it is correct, I graphed the equation and provided the screenshot below. As you can see, the curve passes over the x-axis at the same three points! This tool is amazing for factoring polynomial functions you can’t figure out in your head.
System of Equations Solver
This app also allows you to solve for a system of equations. Say you are given two equations: 5x + 2y = 1, and -3x + y = 0. Of course, this is simple enough that it wouldn’t take to long to solve manually, because there are only 2 equations with 2 unknown variables. However, you may one day encounter 5 equations with 5 unknown variables, and this tool will solve them for you in seconds. Anyways, back to my example, let’s test it! We can leave all the settings alone as long as 2 equations and 2 unknowns are selected. Next, input the system of equations and press graph to solve. If correct, you should find that the conditions x = 1/11 and y = 3/11 satisfies both equations!