### Home > A2C > Chapter 6 > Lesson 6.2.2 > Problem6-76

6-76.

Although the quadratic formula always works as a strategy to solve quadratic equations, for many problems it is not the most efficient method. Sometimes it is faster to factor or complete the square or even just “out-think” the problem. For each equation below, choose the method you think is most efficient to solve the equation and explain your reason. Note that you do not actually need to solve the equation.

1. $x^{2} + 7x − 8 = 0$

Note the expression in this equation can be factored.

1. $\left(x + 2\right)^{2} = 49$

Notice that $49$ is a perfect square.

1. $5x^{2} − x − 7 = 0$

Note the expression in this equation cannot be factored.

1. $x^{2} + 4x = −1$

Adding $4$ to both sides will create a perfect square.