How to Use a Root Solver in Excel

by Ryan Menezes
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Microsoft Excel's solver tool changes the value in one cell to supply a desired result in another on whose contents the first depends. The tool has various practical applications, such as producing sales figures necessary to achieve a target profit. But it also has a pure mathematical application in finding the root, or solution of an equation. This is especially useful for higher order equations that are very difficult to solve manually.

Step 1

Click "File" from Excel's menu bar.

Step 2

Click "Options." The "Excel Options" window will open.

Step 3

Click "Add-Ins" in the left pane. Click "Solver Add-in" from the right pane.

Step 4

Click the "Go" button. The "Add-Ins" dialog box will open.

Step 5

Check the box next to "Solver Add-in." Click "OK."

Step 6

Type your equation into a cell, using a second cell as a reference. For instance, if your equation is "4x^3 + 2x^2 - 87 = -1," type into cell A1, "=4 * A2^3 + 2 * A2^2 - 87."

Step 7

Click on the "Data" ribbon.

Step 8

Click "Solver" from the "Analysis" tab. The "Solver Parameters" window will open.

Step 9

Enter the reference of the cell into which you typed the formula in the "Set Objective:" box. In this example, type "A1."

Step 10

Click the "Value of:" button.

Step 11

Enter your target value in the "Value Of:" box. In this example, type "-1."

Step 12

Type the formula's reference cell in the "By Changing Variable Cells:" box. In this example, type "A2."

Click "Solve." Excel will change both cells accordingly. In this example, cell A1 will change to "-1.00007," which is very close to "-1." Cell A2 will change to "2.623573," which is a root of the equation.

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Ryan Menezes is a professional writer and blogger. He has a Bachelor of Science in journalism from Boston University and has written for the American Civil Liberties Union, the marketing firm InSegment and the project management service Assembla. He is also a member of Mensa and the American Parliamentary Debate Association.