Solve the quadratic equation 2x2+4x=−12

. Which of the following expresses its solutions in the form a±bi
?(1 point)
Responses

−2±2i5–√
negative 2 plus or minus 2 i Start Root 5 End Root

1±i5–√
1 plus or minus i Start Root 5 End Root

−1±i7–√
negative 1 plus or minus i Start Root 7 End Root

−1±i5–√

1 answer

To solve the quadratic equation \( 2x^2 + 4x = -12 \), we first rewrite it in standard form:

\[ 2x^2 + 4x + 12 = 0 \]

Next, we can divide the entire equation by 2 to simplify:

\[ x^2 + 2x + 6 = 0 \]

Now, we'll use the quadratic formula

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

where \( a = 1 \), \( b = 2 \), and \( c = 6 \).

Calculating the discriminant:

\[ b^2 - 4ac = 2^2 - 4 \cdot 1 \cdot 6 = 4 - 24 = -20 \]

Since the discriminant is negative, we will have complex solutions. Now we substitute into the quadratic formula:

\[ x = \frac{-2 \pm \sqrt{-20}}{2 \cdot 1} = \frac{-2 \pm \sqrt{20}i}{2} \]

We can simplify \(\sqrt{20}\):

\[ \sqrt{20} = \sqrt{4 \cdot 5} = 2\sqrt{5} \]

So we substitute this back into our expression:

\[ x = \frac{-2 \pm 2\sqrt{5} i}{2} = -1 \pm \sqrt{5} i \]

Thus, the solutions in the form \( a \pm bi \) are:

\[ -1 \pm i\sqrt{5} \]

From the options given, the correct response from your choices is:

\(-1 \pm i\sqrt{5}\).