Suppose youd like to plot the following equation. To perform a quadratic regression we first need to create a new variable. A quadratic functions variable can take 2 values meaning that there can be 2 solutions.
In the below picture we calculate the roots of the quadratic functions.
Next highlight the values in the range A2B11. First highlight all of the values in column B and drag them to column C. If you need a refresher about the purpose of quadratic regression check out my guide on calculating quadratic regressions in Excel. You can also use Excels Goal Seek feature to solve a quadratic equation.