How do you solve #x^2 = 7x +8# using the quadratic formula?

1 Answer
May 28, 2016

Answer:

8 and -1

Explanation:

#y = x^2 - 7x - 8 = 0#
Solving by shortcut. Since a - b + c = 0, then, the 2 real roots are: -1 and -c/a = 8.
Solving by the improved quadratic formula (Google Search)
#D = d^2 = b^2 - 4ac = 49 + 32 = 81# --> #d = +- 9#
There are 2 real roots:
#x = -b/(2a) +- d/(2a) = 7/2 +- 9/2 = (7 +- 9)/2#
#x = 16/2 = 8# and #x = -2/2 = -1#