# What are common mistakes students make when using the quadratic formula?

Nov 20, 2015

Here are a couple of them.

#### Explanation:

Mistakes in memorization

The denominator $2 a$ is under the sum/difference. It is not just under the square root.

Ignoring signs

If $a$ is positive but $c$ is negative, then ${b}^{2} - 4 a c$ will be the sum of two positive numbers. (Assuming that you have real number coefficients.)