A quadratic function is a type of equation that contains a squared variable. It is called *quadratic* because *quad *means square in Latin. The quadratic functions usually have a structure like ax² + bx + c = 0, where x represents an unknown variable, and a, b, and c represent known constants. In this guide, we are going to show you how to solve quadratic equations in Excel.

Thanks to Excel's features, we can list you 3 different way to solve quadratic equations. These ways includes Goal Seek feature of Excel as well as a manual calculation method and a custom formula which can be created via VBA.

The first part of our guide focuses on *Goal Seek* feature. You can find the manual and VBA methods in the the second part.

## Goal Seek

Goal Seek is among Excel's most important features. Its purpose is exactly what we're looking to do here - to find the variable in an equation. Goal Seek uses an iterative calculation process to "guess" the value of a cell value used in the workbook formulas. Based on this, a quadratic equation can be formulated to be run in Excel. Let's now see how you can do this.

### Creating a quadratic equation in Excel

A quadratic equation should at least have one squared variable. To do this, you can simply multiply the variable by itself, calculate he 2^{nd} power of the variable using the power operator ^ or use the **POWER** function as in our example.

The other important part is to refer a cell as variable, x. Our formula uses named range *x* and *y* for the unknown variables and the formula result respectively (*x* is *C7* and *y* is *D7)*.

**Note:** Although adding *y* into the calculation isn't necessary if you always set it *0*, we included it in our example for versatility.

### Using Goal Seek to solve quadratic equations in Excel

Once the formula is ready in your spreadsheet, it is time to use *Goal Seek* to solve the quadratic function. Follow the steps below to find one of the variables of the equation:

- Select the cell that contains the formula
- Open the
**Goal Seek**dialog in**Data > Data Tools > What-If Analysis > Goal Seek** **Set cell**is the formula cell (It should be automatically selected)**To value**should be 0, which is the right end of the equation- Select the cell of the
**x**value to the**By changing cell** - Click
**OK**to start*Goal Seek* - After Excel finished the
*Goal Seek*execution, the**Goal Seek Status**dialog will display the calculated value - Click
**OK**to close the dialog

### Results of Goal Seek

Although the process is pretty straightforward, there are some downsides to using Goal Seek. As you may have noticed in our screenshots, *Goal Seek* may fail to find the exact value you want. For example, in our example we wanted *Goal Seek* to find a value that makes our formula *0*. However, the value makes the formula return a number close to *0*, *0.000121893*.

If you check the **x **value, you will see a value very close to *-0.2*, *-0.199969528007691*. You need to manually enter *-0.2* to see the formula return *0*.

This difference comes from calculation logic of *Goal Seek*. *Goal Seek* continues searching a certain number of times until it finds a value closer to the target value within the precision limits specified. The default limits for the iteration number and precision value are 100 and 0.001. You can adjust these from **File > Options > Formulas**.

**Note: **Decrease the **Maximum Change** value to increase the *precision*.

Another important point while using *Goal Seek *is that you need to choose (guess) a starting point for *Goal Seek*. *Goal Seek* finds a single variable, but a quadratic function can have 2 variable options. We found *-0.2* value when we set *0* to **x**. If you're satisfied with the results, you can change the **x** and run *Goals Seek* again. For example, setting *10* to **x**, and running *Goal Seek* finds another **x **value, *-1*.

Please see out the second part to see how to solve quadratic equations using regular functions and VBA macros.