*square-root rule:*

Remember that the exponent in a quadratic is never higher than 2 (because it would then no longer be the *square* of an unknown but a cube or something else). An equation that includes the variable *x*^{3} or *x*^{4} is *not* a quadratic.

Also remember to include the plus/minus sign, which indicates that the answer is a positive or negative number. Take the following simple quadratic equation:

Solve 3*x*^{2} + 4 = 31.

- First, isolate the variable by subtracting 4 from each side.
The result is 3

*x*^{2}= 27. - Next, get rid of the 3 by dividing both sides of the equation by 3.
The result is

*x*^{2}= 9. - You can now solve by using the square root rule.