You have learned to solve quadratic equations by four different methods: the even-root property, factoring, completing the square, and the quadratic formula. The even-root property and factoring are limited to certain special equations, but you should use those methods when possible. Any quadratic equation can be solved by completing the square or using the quadratic formula. Because the quadratic formula is usually faster, it is used more often than completing the square. However, completing the square is an important skill to learn.
If our only intent is to obtain the answer, then we would probably use a calculator that is programmed with the quadratic formula. However, by learning different methods, we gain insight into the problem and get valuable practice with algebra. So be sure you learn all of the methods.