A quadratic equation takes the following form:

**ax ^{2} + bx + c = y**

Often you will be given the value for **y** and will be asked to solve for the value of **x**.

For example, suppose we have the following quadratic equation:

**4x ^{2} – 20x + 16 = -8**

It turns out that setting x = **3** or x = **2** will solve this equation.

To solve quadratic equations in Excel, you can use the **Goal Seek** function.

The following step-by-step example shows how to use the Goal Seek function in practice.

**Step 1: Enter the Equation**

First, let’s enter some random value for x and the formula for the quadratic equation for y:

**Step 2: Find the First X Value Using Goal Seek**

Next, click the **Data** tab along the top ribbon, then click the **What-If Analysis** button, then **Goal Seek**:

In the new window that appears, specify that you’d like to set cell **B2** equal to **-8** by changing the value in cell **A2**:

Once we click **OK**, the Goal Seek function will automatically find the value for x that solves the equation:

Goal Seek finds that the value **x=2** (assuming 1.9999 rounds to 2) solves the quadratic equation.

**Step 3: Find the Second X Value Using Goal Seek**

To find the second x value that solves the quadratic equation, set the initial x-value to a different number.

For example, we could choose to set the initial x-value to 4:

We can then run the **Goal Seek** function again and see that it finds a new solution of **x=3**:

Thus, the two x-values that can solve this quadratic equation are **x=2** and **x=3**.

**Additional Resources**

The following tutorials explain how to perform other common tasks in Excel:

How to Solve a System of Equations in Excel

How to Plot an Equation in Excel