Question

Solve using quadratic formula x squared -2x-8=0

Answer 1

$x= \frac{-b\pm \sqrt{b^2-4ac} }{2a}$ for the equation $ax^2+bx+c$

Your question is $x^2-2x-8=0$

So $a=1 \\b=-2\\c=-8$

So plug in your numbers:
$x= \frac{-(-2)\pm \sqrt{(-2)^2-4(1)(-8)} }{2(1)}$

Simplify:
$x= \frac{2\pm \sqrt{4-(-32)} }{2}$

Simplify a little more:
$\frac{2\pm6}{2}$

So our answer is<u />
$x= \frac{2+ 6 }{2} = 4\\x= \frac{2- 6 }{2}=-2$

So $x=4, x=-2$

Answer 2

X² - 2x - 8 = 0
x = -(-2) +/- √((-2)² - 4(1)(-8))
                      2(1)
x = 2 +/- √(4 + 32)
                 2
x = 2 +/- √(36)
              2
x = 2 +/- 6
           2
x = 1 +/- 3
x = 1 + 3      x = 1 - 3
x = 4            x = -2