Another way to solve tricky quadratic equations aside from completing the square is by using the quadratic formula.
For example, to solve the below equation, we would have to use the quadratic equation. Some questions will ask you to give your answer to 3 significant figures or in surd form. For the purposes of this example, we will write the answer in surd form.
If you are asked to give the answer to 3 significant figures, the answer would be like below.