Video lesson: Solving polynomial equations on the TI-Nspire

By Tech Powered Dad | August 28, 2010

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 the built in features features of a TI-Nspire to solve a polynomial equation. This lesson does require that you have TI-Nspire OS 2.0 or above.  If you don’t, check out our tutorial on upgrading the TI-Nspire OS.

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 Nspire.  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, , 8, and -2.

The other catch is that you won’t get the solutions in radical form if you are using a regular Nspire, only with an Nspire CAS. 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 Nspire to check that answer instead.

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