The *plus or minus sign* is used to indicate that the value to its can be either added or subtracted to the value to its left. For example, is a way of writing or using just one expression. To write this symbol with MathQuill, type \pm and then a space.

The *quadratic formula* is a formula that can be used to find solutions to quadratic equations. If a quadratic equation is written in the form , then the quadratic formula states that its solutions will be:

A *root* of a polynomial, also called a *zero* of a polynomial, is a value of that makes the polynomial equal to 0. For a polynomial equation, if a root is a real number, then this tells us the -coordinate of one of the graphs’ -intercepts. Solutions to the quadratic formula, for example, tell us the roots of quadratic equations.
Let’s say that we have the equation . We can factor this to be . If we set , then the values that solve the quadratic equation are the roots of the polynomial equation, and .