To solve a quadratic equation means to find all the roots of the quadratic equations.
Example:
Find the roots of the quadratic equations
a. $${x^2} = 9$$
b. $${2x^2} - 98 = 0$$
$\begin{array}{l} {x^2} = 9\\ x = \pm \sqrt 9 \\ x = \pm 3 \end{array}$ b.
$\begin{array}{l} 2{x^2} - 98 = 0\\ 2{x^2} = 98\\ {x^2} = \frac{{98}}{2} = 49\\ x = \pm \sqrt {49} = \pm 7 \end{array}$