Question

How do you solve `x^2 = 5x + 8` using the quadratic formula?

Answer 1

`(5 +- sqrt57)/2`

Explanation:

Bring the equation to standard form:
`y = x^2 - 5x - 8 = 0`
Use the improved quadratic formula (Google, Yahoo Search).
`D = d^2 = b^2 - 4ac = 25 + 32 = 57` --> `d = +- sqrt57`
There are 2 real roots:
`x = -b/(2a) +- d/(2a) = 5/2 +- sqrt57/2 = (5 +- sqrt57)/2`