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Let us go down to earth using numerical example, suppose you want to find the real root of this polynomial cubic equation

The spreadsheet example of thi stutorial can be downloaded here.

Here is how to do it steps by step:

1. Firstly, input the coefficient of the equations in separate cells (B4:E4).

2. Then, you may guess the value of x with any number as initial value (B6).

3. After that, type the equation of polynomial (G4).

The screen is shown in the figure below

4. From the menu of MS Excel, click **Tools-Goal Seek **… and Goal Seek dialog show up.

5. Set cell G4 ( *the equation *) to value 0 ( *target value *) by changing cell $B$6 ( *initial guess of x *) and click OK button.

6. The result is shown in the figure below. The real root is 0.5795 when y is approximately zero (-5E-06 = -0.0000050)

Note that for other cases, the result may varies depend on the initial condition.

See also:

Goal Seek Tutorial, MS Excel Tutorial index, Kardi Teknomo's Tutorial

Send your comments, questions and
suggestions

**Preferable reference for this tutorial is**

Teknomo, Kardi (2015) Finding Root of Polynomial Using Microsoft Excel. http:\\people.revoledu.com\kardi\ tutorial\Excel\RootPolynomial.html