Question

Solve x2 + 4x + 8 = 0. (2 points)



1. x equals negative 2 plus or minus 2 I
2. x equals negative 2 plus or minus 4 I
3. x equals negative 4 plus or minus 2 I
4. x equals negative 4 plus or minus 4 I

Answer 1

The correct answer is option #1. x = -2 +/- 2i

We can find this by using the quadratic equation, which is written below. 

$\frac{-b +/- \sqrt{ b^{2} -4ac} }{2a}$

Now we know the a, b and c values by looking at the equation. a is always the number attached to x^2 (which is 1), b is always the number attached to x (which is 4) and c is the number with no variable (which is 8). So we can place them in in the appropriate spots in the equation. 

$\frac{-b +/- \sqrt{ b^{2} -4ac} }{2a}$

$\frac{-4 +/- \sqrt{ 4^{2} -4(1)(8)} }{2(1)}$

$\frac{-4 +/- \sqrt{ 16 - 32} }{2}$

$\frac{-4 +/- \sqrt{ -16} }{2}$

$\frac{-4 +/- 4i }{2}$

-2 +/- 2i

Answer 2

Answer:

x = -2 +/- 2i

(Took the test just now, hope this helps ! Good luck :) !  )