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Solve 2x² + 11x + 4 = 0

The solutions of 2x² + 11x + 4 = 0 are x = (-11 + √89)/4 or x = (-11 - √89)/4, that is x ≈ -0.39150472 and x ≈ -5.1084953.

x² +x += 0
2x2+11x+4=0⇒x=−11+894, −11−8942x^2 + 11x + 4 = 0 \Rightarrow x = \frac{-11 + \sqrt{89}}{4},\ \frac{-11 - \sqrt{89}}{4}
Discriminant D = 89 · x ≈ -0.391505, -5.1085

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

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Graph of y = 2x² + 11x + 4-7-6-5-4-3-2-112-1010203040x = -0.39150472x = -5.1084953vertexy = 2x² + 11x + 4
Graph of y = 2x² + 11x + 4. The curve crosses the x-axis at x = -0.39150472 and x = -5.1084953; the vertex is at (-2.75, -11.125).

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 = 4.

    2x2+11x+4=02x^2 + 11x + 4 = 0
  2. 2

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

    D=112−4⋅2⋅4=121−32=89D = 11^2 - 4\cdot2\cdot4 = 121 - 32 = 89
  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±894x = \frac{-b \pm \sqrt{D}}{2a} = \frac{-11 \pm \sqrt{89}}{4}
  5. 5

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

    x=−11+894orx=−11−894x = \frac{-11 + \sqrt{89}}{4}\quad\text{or}\quad x = \frac{-11 - \sqrt{89}}{4}
  6. 6

    As decimals: x ≈ -0.39150472 and x ≈ -5.1084953.

  7. 7

    Check numerically: for x ≈ -0.39150472 the left side is -8.8817842e-16 (zero up to rounding) ✓

LaTeX source of the formulas on this page
\[ 2x^2 + 11x + 4 = 0\ \Rightarrow\ x = \frac{-11 + \sqrt{89}}{4},\ \frac{-11 - \sqrt{89}}{4} \]
\[ 2x^2 + 11x + 4 = 0 \]
\[ D = 11^2 - 4\cdot2\cdot4 = 121 - 32 = 89 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} = \frac{-11 \pm \sqrt{89}}{4} \]
\[ x = \frac{-11 + \sqrt{89}}{4}\quad\text{or}\quad x = \frac{-11 - \sqrt{89}}{4} \]

The parabola y = 2x² + 11x + 4

xy
-5.756.875
-4.75-3.125
-3.75-9.125
-2.75-11.125
-1.75-9.125
-0.75-3.125
0.256.875

Questions

What are the solutions of 2x² + 11x + 4 = 0?

The solutions of 2x² + 11x + 4 = 0 are x = (-11 + √89)/4 or x = (-11 - √89)/4, that is x ≈ -0.39150472 and x ≈ -5.1084953.

Does 2x² + 11x + 4 = 0 factor?

Not over the integers, because the discriminant 89 is not a perfect square. Use the quadratic formula.

What is the vertex of y = 2x² + 11x + 4?

(-11/4, -89/8). 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 = 2.

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    Solve 2x² + 11x + 4 = 0: x = (-11 + √89)/4 or x = (-11 - √89)/4 (steps) | WordGPT