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Solve x² - 8x + 3 = 0

The solutions of x² - 8x + 3 = 0 are x = 4 + √13 or x = 4 - √13, that is x ≈ 7.6055513 and x ≈ 0.39444872.

x² +x += 0
x2−8x+3=0⇒x=4+13, 4−13x^2 - 8x + 3 = 0 \Rightarrow x = 4 + \sqrt{13},\ 4 - \sqrt{13}
Discriminant D = 52 · x ≈ 7.60555, 0.394449

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

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Graph of y = x² - 8x + 3-2246810-101020x = 7.6055513x = 0.39444872vertexy = x² - 8x + 3
Graph of y = x² - 8x + 3. The curve crosses the x-axis at x = 7.6055513 and x = 0.39444872; the vertex is at (4, -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 = -8, c = 3.

    x2−8x+3=0x^2 - 8x + 3 = 0
  2. 2

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

    D=(−8)2−4⋅1⋅3=64−12=52D = (-8)^2 - 4\cdot1\cdot3 = 64 - 12 = 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=8±522x = \frac{-b \pm \sqrt{D}}{2a} = \frac{8 \pm \sqrt{52}}{2}
  5. 5

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

    x=4+13orx=4−13x = 4 + \sqrt{13}\quad\text{or}\quad x = 4 - \sqrt{13}
  6. 6

    As decimals: x ≈ 7.6055513 and x ≈ 0.39444872.

  7. 7

    Check numerically: for x ≈ 7.6055513 the left side is 0 (zero up to rounding) ✓

LaTeX source of the formulas on this page
\[ x^2 - 8x + 3 = 0\ \Rightarrow\ x = 4 + \sqrt{13},\ 4 - \sqrt{13} \]
\[ x^2 - 8x + 3 = 0 \]
\[ D = (-8)^2 - 4\cdot1\cdot3 = 64 - 12 = 52 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} = \frac{8 \pm \sqrt{52}}{2} \]
\[ x = 4 + \sqrt{13}\quad\text{or}\quad x = 4 - \sqrt{13} \]

The parabola y = x² - 8x + 3

xy
1-4
2-9
3-12
4-13
5-12
6-9
7-4

Questions

What are the solutions of x² - 8x + 3 = 0?

The solutions of x² - 8x + 3 = 0 are x = 4 + √13 or x = 4 - √13, that is x ≈ 7.6055513 and x ≈ 0.39444872.

Does x² - 8x + 3 = 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 - 8x + 3?

(4, -13). The parabola opens upwards, so this is the minimum.

What are the sum and product of the roots?

Sum = −b/a = 8, product = c/a = 3.

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    Solve x² - 8x + 3 = 0: x = 4 + √13 or x = 4 - √13 (steps) | WordGPT