Newton Raphson Method in Excel
The Newton-Raphson method is a numerical method used to find the roots of an equation, i.e., the values of x that make the equation equal to zero. It is a powerful tool for solving complex non-linear equations, and it can be implemented in Excel using a combination of the “Goal Seek” function and a user-defined function.
The Newton-Raphson method is based on the idea of iteratively improving an estimate of the root, based on the tangent line to the curve of the equation at the current estimate. The method starts with an initial guess for the root, and then calculates a new estimate.
Follow the steps below to learn how to use Newton Raphson Method in Excel.
Newton Raphson Method to solve the equation
We are going to use the Newton Method to solve the equation x^2=5
To implement the Newton Raphson Method in Excel, first you need to label the columns with appropriate headers like this.
Note: Argument (x) is required for a column for function evaluations (f(x)), and a column for slope (f\’(x)).
Preparing Newton’s method calculator
Fill in your initial guess value in the x column (x).
In column B write the formula =A2^2-5 and in column C write the formula 2*A2
In column A cell A3 enter the formula =A2-B2/C2. Select cell B2, move the cursor to the bottom right, a black plus sign will appear. Drag the black plus sign to cell B7.
Copy this formula down to the next row in cell C2 to continue the Newton Raphson iteration.
Repeat with cell A1. That’s it. You have now learned how to use the Newton Method in Excel.
Note that once the value of x no longer varies from row to row and f(x) is small (close to zero), you have the solution (assuming the process has converged).
Note: Answer is shaded in yellow.
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