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Solve -x² - 7x - 10 = 0

The solutions of -x² - 7x - 10 = 0 are x = -5 or x = -2.

x² +x += 0
−x2−7x−10=0⇒x=−5, −2-x^2 - 7x - 10 = 0 \Rightarrow x = -5,\ -2
Discriminant D = 9 · x ≈ -5, -2

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

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Graph of y = -x² - 7x - 10-7-6-5-4-3-2-1-14-12-10-8-6-4-224x = -5x = -2vertexy = -x² - 7x - 10
Graph of y = -x² - 7x - 10. The curve crosses the x-axis at x = -5 and x = -2; the vertex is at (-3.5, 2.25).

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 = -7, c = -10.

    −x2−7x−10=0-x^2 - 7x - 10 = 0
  2. 2

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

    D=(−7)2−4⋅(−1)⋅(−10)=49−40=9D = (-7)^2 - 4\cdot(-1)\cdot(-10) = 49 - 40 = 9
  3. 3

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

  4. 4

    Method 1, factoring. The roots are rational, so the left side factors:

    −(x+5)(x+2)=0-\left(x + 5\right)\left(x + 2\right) = 0
  5. 5

    A product is zero when one of its factors is zero, so set each factor equal to 0 and solve:

    x+5=0⇒x=−5x+2=0⇒x=−2x + 5 = 0 \Rightarrow x = -5\qquad x + 2 = 0 \Rightarrow x = -2
  6. 6

    Method 2, The quadratic formula works for every quadratic:

    x=−b±D2a=7±9−2x = \frac{-b \pm \sqrt{D}}{2a} = \frac{7 \pm \sqrt{9}}{-2}
  7. 7

    Simplify to get the solutions:

    x=−5orx=−2x = -5\quad\text{or}\quad x = -2
  8. 8

    Check by putting x = -5 back in: a·x² + b·x + c = -1·(25) + (-7)·(-5) + (-10) = 0 ✓

LaTeX source of the formulas on this page
\[ -x^2 - 7x - 10 = 0\ \Rightarrow\ x = -5,\ -2 \]
\[ -x^2 - 7x - 10 = 0 \]
\[ D = (-7)^2 - 4\cdot(-1)\cdot(-10) = 49 - 40 = 9 \]
\[ -\left(x + 5\right)\left(x + 2\right) = 0 \]
\[ x + 5 = 0 \Rightarrow x = -5\qquad x + 2 = 0 \Rightarrow x = -2 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} = \frac{7 \pm \sqrt{9}}{-2} \]
\[ x = -5\quad\text{or}\quad x = -2 \]

The parabola y = -x² - 7x - 10

xy
-6.5-6.75
-5.5-1.75
-4.51.25
-3.52.25
-2.51.25
-1.5-1.75
-0.5-6.75

Questions

What are the solutions of -x² - 7x - 10 = 0?

The solutions of -x² - 7x - 10 = 0 are x = -5 or x = -2.

Does -x² - 7x - 10 = 0 factor?

Yes: -1(x+5)(x+2) = 0.

What is the vertex of y = -x² - 7x - 10?

(-7/2, 9/4). The parabola opens downwards, so this is the maximum.

What are the sum and product of the roots?

Sum = −b/a = -7, product = c/a = 10.

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