How to solve this quadratic equation with the quadratic formula?

Question

I've been having trouble with this problem:

 

x2 + 2x = 8

 

So far this is what I got:

 

-2±√-28
-----------
      2

 

However I'm not too sure what to do next, help?

Answer 1

x² +2x-8=0

 

using formula x= -b ±√b² -4ac  /2a

 

x= -2 ±√4-4*(1)(-8) / 2

  

  = -2±√36 /2

  =-2 ±6 /2

x= -2+6 /2  or x= -2 -6 /2

    =2                 =-4

Answer 2

x² + 2x = 8   (subtract 8 from both sides so the quadratic function is equal to zero)

x² + 2x - 8 = 0 (either factor & solve OR use the quadratic formula)

 

Factor & Solve using Zero Product Property:

(x + 4)(x - 2) = 0 (use zero product rule to solve: if the product of two numbers is zero then one of those numbers is zero)

x + 4 = 0  or  x - 2 = 0

x = -4   or  x = 2

 

or

 

Quadratic Formula:

x = [-2± √(2² - 4(1)(-8)&nbsp)] / ((2)(1))

x= (-2 ±√(4+32) ) /2 = (-2± √36) /2 

x= (-2+6)/2 or (-2 -6)/2  = 4/2  or -8/2

x= 2 or -4