How to Use Excel to Solve a Polynomial

Written by stephanie ellen
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How to Use Excel to Solve a Polynomial
You'll have to solve polynomials in high school math classes. (math image by jaddingt from Fotolia.com)

A polynomial in mathematics is the sum of a number of terms that are added, subtracted, or multiplied. A polynomial can have one term like 1, x, y, or z, or it can have multiples terms: for example, x^3 + 10 ^ 2 + 4 is a polynomial. Solving a polynomial means that you have to find a value for the X in the equation. This is sometimes called finding a root of a polynomial or finding the zeros. Excel can do this task for you.

Skill level:
Easy

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Things you need

  • Excel 2007 or Excel 2010

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Instructions

  1. 1

    Input the coefficients into separate cells in row 4 in Excel, starting at cell "B4." for example, if you have a cubic equation x^3 - 2x^2 - 3x, then your coefficients are 1, -2, 6 and -3. Click on cell "B4" and type "1", then click on cell "C4" and type "-2," then click on cell "D4" and type "6," then click on cell "E4" and type "-3."

  2. 2

    Click on cell "B6" and type a guess for the value of X. If you have no idea of what the value might be, just type "0."

  3. 3

    Click on cell "G4" and then type the full equation into the cell. In this example, the equation would be "x^3 - 2x^2 - 3x."

  4. 4

    Click on the "Data" tab, then click on "What-If Analysis," in the Data Tools group and then click "Goal Seek."

  5. 5

    Click on the "Set cell" text box and type "G4."

  6. 6

    Click on the "To value" text box and then type "0."

  7. 7

    Click on the "By changing cell" text box and then type "$B$6."

  8. 8

    Click on "OK." Excel will solve the polynomial and return the result in cell B6 (the initial guess box).

Tips and warnings

  • Make sure that the polynomial you enter is actually a polynomial. If your equation has any division in it, or if your exponents are negative, the equation is not a polynomial and therefore the Excel Goal Seek function will either return an error or it may return a wrong answer.

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