#### Answer

Solving a quadratic equation means finding the value of $x$ that makes the expression $a x^2 + b x + c =0$ true. The methods can either be by factoring, completing the square, or by using the quadratic formula.
Since all equations can be solved by using the quadratic formula, it may be beneficial to first determine the discriminant. This will provide information on the number of solutions, and whether these solutions are real numbers.
If the discriminant yields a negative number, then $only$ the quadratic formula can be used. Otherwise, factoring or completing the square can be used.