Use the quadratic formula to solve $x^2-4x-8=0$.
- $2 \pm 2\sqrt 3$
- $1 \pm \sqrt 3$
- $3-3\sqrt 3$
-
None of these
Reveal answer
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A
Correct answer
Explanation
Using the quadratic formula x = (-b +/- sqrt(b^2 - 4ac)) / 2a for x^2-4x-8=0, we get x = (4 +/- sqrt(16 - 4(1)(-8))) / 2 = (4 +/- sqrt(48)) / 2 = (4 +/- 4sqrt(3)) / 2 = 2 +/- 2sqrt(3).
AI explanation
Using the quadratic formula, x equals negative b plus or minus the square root of b squared minus 4ac all divided by 2a. Substitute a equals 1, b equals negative 4, and c equals negative 8 to get x equals 4 plus or minus the square root of 16 plus 32 divided by 2. This simplifies to 4 plus or minus the square root of 48 divided by 2, which results in x equals 2 plus or minus 2 times the square root of 3.