Question

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

Answer 1

Use the quadratic formula. a = 1, b = 4, c = 8.

\[x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\] and \[\sqrt{-x} = i\sqrt{x}\]

Answer 2

ive tried i don't understand it

Answer 3

You just to plug in the numbers.

\[x = \frac{-(4) \pm \sqrt{4^2-4(1)(8)}}{2(1)} = \frac{-4 \pm \sqrt{-16}}{2}\]

Answer 4

What is \[\sqrt{-16}\]

Answer 5

\[\sqrt{-16}=\sqrt{(-1)(16)}=\sqrt{-1}*\sqrt{16}\]
\[\sqrt{-1} = i\]so\[\sqrt{-16}=i\sqrt{16}=4i\]

Combine that with the expression for x we previously got.

Answer 6

\[\frac{-4 \pm \sqrt{-16}}{2} = \frac{-4 \pm 4i}{2} \]

and you should be able to figure out which of the answers is equal to that.