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Solve 2x² + 11x + 7 = 0

The solutions of 2x² + 11x + 7 = 0 are x = (-11 + √65)/4 or x = (-11 - √65)/4, that is x ≈ -0.73443556 and x ≈ -4.7655644.

x² +x += 0
2x2+11x+7=0⇒x=−11+654, −11−6542x^2 + 11x + 7 = 0 \Rightarrow x = \frac{-11 + \sqrt{65}}{4},\ \frac{-11 - \sqrt{65}}{4}
Discriminant D = 65 · x ≈ -0.734436, -4.76556

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

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Graph of y = 2x² + 11x + 7-7-6-5-4-3-2-11-10102030x = -0.73443556x = -4.7655644vertexy = 2x² + 11x + 7
Graph of y = 2x² + 11x + 7. The curve crosses the x-axis at x = -0.73443556 and x = -4.7655644; the vertex is at (-2.75, -8.125).

How to work it out

  1. 1

    Write it in standard form a x² + b x + c = 0 and read off the coefficients: a = 2, b = 11, c = 7.

    2x2+11x+7=02x^2 + 11x + 7 = 0
  2. 2

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

    D=112−4⋅2⋅7=121−56=65D = 11^2 - 4\cdot2\cdot7 = 121 - 56 = 65
  3. 3

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

  4. 4

    The quadratic formula works for every quadratic:

    x=−b±D2a=−11±654x = \frac{-b \pm \sqrt{D}}{2a} = \frac{-11 \pm \sqrt{65}}{4}
  5. 5

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

    x=−11+654orx=−11−654x = \frac{-11 + \sqrt{65}}{4}\quad\text{or}\quad x = \frac{-11 - \sqrt{65}}{4}
  6. 6

    As decimals: x ≈ -0.73443556 and x ≈ -4.7655644.

  7. 7

    Check numerically: for x ≈ -0.73443556 the left side is -8.8817842e-16 (zero up to rounding) ✓

LaTeX source of the formulas on this page
\[ 2x^2 + 11x + 7 = 0\ \Rightarrow\ x = \frac{-11 + \sqrt{65}}{4},\ \frac{-11 - \sqrt{65}}{4} \]
\[ 2x^2 + 11x + 7 = 0 \]
\[ D = 11^2 - 4\cdot2\cdot7 = 121 - 56 = 65 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} = \frac{-11 \pm \sqrt{65}}{4} \]
\[ x = \frac{-11 + \sqrt{65}}{4}\quad\text{or}\quad x = \frac{-11 - \sqrt{65}}{4} \]

The parabola y = 2x² + 11x + 7

xy
-5.759.875
-4.75-0.125
-3.75-6.125
-2.75-8.125
-1.75-6.125
-0.75-0.125
0.259.875

Questions

What are the solutions of 2x² + 11x + 7 = 0?

The solutions of 2x² + 11x + 7 = 0 are x = (-11 + √65)/4 or x = (-11 - √65)/4, that is x ≈ -0.73443556 and x ≈ -4.7655644.

Does 2x² + 11x + 7 = 0 factor?

Not over the integers, because the discriminant 65 is not a perfect square. Use the quadratic formula.

What is the vertex of y = 2x² + 11x + 7?

(-11/4, -65/8). The parabola opens upwards, so this is the minimum.

What are the sum and product of the roots?

Sum = −b/a = -11/2, product = c/a = 7/2.

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    Solve 2x² + 11x + 7 = 0: x = (-11 + √65)/4 or x = (-11 - √65)/4 (steps) | WordGPT