WEBVTT

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Here is the problem: x squared plus 4x plus 13 equals 0.

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A quadratic equation in x: solve with the quadratic formula.

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Start with the equation.

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Move every term to one side to get standard form.

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Compute the discriminant.

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delta less than 0, so there are no real roots; the two roots are complex conjugates.

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Apply the quadratic formula with the square root of negative 1 equals i.

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Simplify.

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So the answer is x equals negative 2 minus 3i or x equals negative 2 plus 3i.

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The discriminant is negative, so there are no real solutions; the solutions are a pair of complex conjugates.

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Vieta: sum of roots equals negative 4 equals negative b/a equals negative 4; product equals 13 equals c/a equals 13.