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Solve -x² - 2x + 12 = 0

The solutions of -x² - 2x + 12 = 0 are x = -1 + √13 or x = -1 - √13, that is x ≈ -4.6055513 and x ≈ 2.6055513.

x² +x += 0
−x2−2x+12=0⇒x=−1+13, −1−13-x^2 - 2x + 12 = 0 \Rightarrow x = -1 + \sqrt{13},\ -1 - \sqrt{13}
Discriminant D = 52 · x ≈ -4.60555, 2.60555

Change a, b or c (whole numbers, a not 0) and the exact solutions follow.

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Graph of y = -x² - 2x + 12-6-4-224-25-20-15-10-551015x = -4.6055513x = 2.6055513vertexy = -x² - 2x + 12
Graph of y = -x² - 2x + 12. The curve crosses the x-axis at x = -4.6055513 and x = 2.6055513; the vertex is at (-1, 13).

How to work it out

  1. 1

    Write it in standard form a x² + b x + c = 0 and read off the coefficients: a = -1, b = -2, c = 12.

    −x2−2x+12=0-x^2 - 2x + 12 = 0
  2. 2

    Work out the discriminant D = b² − 4ac. Its sign tells you how many real solutions there are.

    D=(−2)2−4⋅(−1)⋅12=4+48=52D = (-2)^2 - 4\cdot(-1)\cdot12 = 4 + 48 = 52
  3. 3

    D is positive, so there are two different real solutions.

  4. 4

    The quadratic formula works for every quadratic:

    x=−b±D2a=2±52−2x = \frac{-b \pm \sqrt{D}}{2a} = \frac{2 \pm \sqrt{52}}{-2}
  5. 5

    Simplify (pull the square out of the root) to get the solutions:

    x=−1+13orx=−1−13x = -1 + \sqrt{13}\quad\text{or}\quad x = -1 - \sqrt{13}
  6. 6

    As decimals: x ≈ -4.6055513 and x ≈ 2.6055513.

  7. 7

    Check numerically: for x ≈ -4.6055513 the left side is -3.5527137e-15 (zero up to rounding) ✓

LaTeX source of the formulas on this page
\[ -x^2 - 2x + 12 = 0\ \Rightarrow\ x = -1 + \sqrt{13},\ -1 - \sqrt{13} \]
\[ -x^2 - 2x + 12 = 0 \]
\[ D = (-2)^2 - 4\cdot(-1)\cdot12 = 4 + 48 = 52 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} = \frac{2 \pm \sqrt{52}}{-2} \]
\[ x = -1 + \sqrt{13}\quad\text{or}\quad x = -1 - \sqrt{13} \]

The parabola y = -x² - 2x + 12

xy
-44
-39
-212
-113
012
19
24

Questions

What are the solutions of -x² - 2x + 12 = 0?

The solutions of -x² - 2x + 12 = 0 are x = -1 + √13 or x = -1 - √13, that is x ≈ -4.6055513 and x ≈ 2.6055513.

Does -x² - 2x + 12 = 0 factor?

Not over the integers, because the discriminant 52 is not a perfect square. Use the quadratic formula.

What is the vertex of y = -x² - 2x + 12?

(-1, 13). The parabola opens downwards, so this is the maximum.

What are the sum and product of the roots?

Sum = −b/a = -2, product = c/a = -12.

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    Solve -x² - 2x + 12 = 0: x = -1 + √13 or x = -1 - √13 (steps) | WordGPT