Question

Solve this quadratic equation using the quadratic formula.

x2 + 8x - 5 = 0

Answer 1

- b +/- root(b^2 - 4ac)
x = ----------------------
2a

- (8) +/- root(8^2 - 4(1)(-5) -8 +/- root(64 + 20)
x = -------------------------- = --------------------
2*1 2

-8 +/- root84 -8 +/- 2root21
x = -------------- = --------------
2 2

Answer 2

-8 + 2root21 -8 - 2root21
x = ------------- or ------------
2 2


2(-4 + root21) 2(-4 - root21)
x = --------------- or -------------
2 2

Answer 3

so final answer

\[x = -4 + \sqrt{21}\]
or

Answer 4

\[x = -4 -\sqrt{21}\]