How do you solve -x^2 + 5x - 9 = 0?

1 Answer
Aug 18, 2016

(5 +- isqrt11)/2

Explanation:

y = - x^2 + 5x - 9 = 0
Use the improved quadratic formula (Socratic Search):
D = d^2 = b^2 - 4ac = 25 - 36 = - 11.
There are no real roots because D < 0. There are 2 imaginary roots.
D = 11i^2 --> d = +- isqrt11

x = - b/(2a) +- d/(2a) = -5/-2 +- isqrt11/2 = (5 +- isqrt11)/2