How to Solve an Equation in Excel

This week at the Chandoo,org Forums, Usman asked, “ I have a curve. I did its fitting using Excel and got an equation. y = 2E+07x^-2.146 For y=60 what will be the value of x? How can we solve this equation using Excel? ” Lets look at how this can be solved using Excel. Define the Problem Usman formula is y = 2E+07x^-2.146 or expanded y = 2*10^7*x^-2.146 We can use Excel’s Goal Seek function to assist us here Goal Seek is located in the Data, What-If Analysis, Goal Seek menu Goal Seek is an inbuilt function in Excel that searches for a solution to a model/formula by iteratively trying source cell values until a solution is found. Before we start, Excel doesn’t understand the concepts of x and y, but we can use cells for these instead To use Goal Seek we need to put our formula into a cell. Start a new file and in C3 (our y cell) type:  = 2*10^7*B3^-2.146 In B3 (our x cell): Put a value say 10 Note that C3 will show the solution of the formula for when x=10 or = 2*10^7*10^-2.146 = 142,899.277 Using Goal Seek To use Goal Seek to find what value of x (B3) will result in y (C3) = 60, Select C3 Goto the Data, What-If Analysis, Goal Seek menu Set Cell: C3  – This is our y value cell To value: 60  This is the value we want to achieve By changing cell: B3 – This is our x value cell Click OK when ready Excel shows us that it has found a solution and that y (C3) =60 when x (B3) = 374.60 Select OK to save the result Select Cancel to return to the previous value You can download a sample of the above here: Download Sample File How have you solved Formulas using Excel or other techniques How have you solved Formulas using Excel or other techniques? Let us know in the comments below: Learn more about Goal seek and solver: Introduction to Goal seek and building a retirement calendar Introduction to Solver Using solver to assign items to buckets