Video lesson: Solving polynomial equations on the TI-84

When you are solving a quadratic equation, you have a lot of options. You can factor, complete the square, or use the quadratic formula. But what about polynomials with a degree (highest exponent) that is higher than two? These can be difficult to factor with the types of factoring you learn in a high school algebra class. This video lesson explains how you can use an app included with the TI-84+ Silver Edition  to solve a polynomial equation.

There are a couple of catches with using the method described in the video. First, if you have an equation that “skips” a power of x, you still have to include it as a 0 for the TI-84 plus.  For example, if you have the equation:

x^3 + 8x -2 = 0

It’s like the “squared term” of x was skipped.  That means you would enter the polynomial’s coefficients as 1, 0, 8, and -2.

The other catch is that you won’t get the solutions in radical form. Instead the answers will be returned as decimals. That won’t be enough for a lot of teachers, who will want to see the square root in the answer. Still, if you calculate the answer to the question by hand on a quiz or test, you can still convert that radical answer to a decimal and then use the TI-84 to check that answer instead.

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Lucas Allen

Lucas Allen

For more than a decade, Lucas Allen was a high school math teacher and math team coach in Illinois. His 2012 Morton High School math team won the Illinois state championship. Recently, he made the jump from public education to the corporate world and is now working as a data scientist. He is interested in just about all forms of technology, including the TI-Nspire, Nexus devices, R, MOOCs, and more. You can follow , and if you are nice, he will probably follow you back.

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