Solve the quadratic equation 2x2+4x=−12 . Which of the following expresses its solutions in the form a±bi ?(1 point)

Responses

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

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

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

−2±2i5–√

1 answer

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

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

Next, we can simplify the equation by dividing all terms by 2:

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

Now we can use the quadratic formula \(x = \frac{{-b \pm \sqrt{{b^2 - 4ac}}}}{{2a}}\), where \(a = 1\), \(b = 2\), and \(c = 6\).

Calculate the discriminant (\(b^2 - 4ac\)):

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

Since the discriminant is negative, we will have complex solutions. Now, we compute the solutions:

\[ x = \frac{{-2 \pm \sqrt{{-20}}}}{{2(1)}} \] \[ x = \frac{{-2 \pm \sqrt{{20}}i}}{{2}} \] \[ x = \frac{{-2 \pm 2\sqrt{5}i}}{{2}} \] \[ x = -1 \pm \sqrt{5}i \]

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

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

From the options provided, the solution that matches is:

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