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

1 Answer
Nghi N.
Jul 19, 2016

(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

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