# How do you solve using the quadratic formula x^2 + x - 42 = 0?

Apr 30, 2015

x=6, -7

Compare the given equation with $a {x}^{2} + b x + c = 0$ and determine a=1, b=1 and c= -42. Plug these values in the quadratic formula x= $\frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$

x= $\frac{- 1 \pm \sqrt{1 + 168}}{2}$

= $\frac{- 1 \pm 13}{2}$

x=6, -7

May 2, 2015

There is another way. Use the new AC Method.
y = x^2 + x - 42.
Compose factor pairs of c = -42. Proceed: (-1, 42)(-2, 21)(-3, 14)(-6, 7).
This last sum is -6 + 7 = 1 = b. Then, the 2 real roots are: 6 and -7.