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How do you find the remaining zeros using synthetic division?

Published in Polynomial Zeros 2 mins read

After performing synthetic division, you find the remaining zeros by setting the resulting quotient equal to zero and solving for x. This quotient will be a polynomial with a degree one less than the original polynomial.

Here's a breakdown of the process, incorporating information from the provided reference:

  1. Perform Synthetic Division: Use synthetic division to divide the polynomial by a known zero (root). This will reduce the degree of the polynomial.

  2. Write the Quotient: The result of the synthetic division gives you the coefficients of the new polynomial (the quotient). For example, the video reference mentions that if you start with an x cubed polynomial and perform synthetic division, the result will be an x squared polynomial.

  3. Set the Quotient to Zero: Take the quotient polynomial and set it equal to zero. This creates an equation that you can solve for the remaining zeros.

    • Example (from reference): If after synthetic division you have 1x² + 0x + 4, you would set up the equation x² + 4 = 0.
  4. Solve for x: Solve the resulting equation for x. The solutions are the remaining zeros of the original polynomial.

    • In the example above (x² + 4 = 0), you would subtract 4 from both sides (x² = -4) and then take the square root of both sides (x = ±2i). This means the remaining zeros are 2i and -2i.

In summary, synthetic division simplifies the polynomial, and then solving the resulting quotient allows you to find the remaining zeros.

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