Solve 2x² - 10x - 12 = 0
The solutions of 2x² - 10x - 12 = 0 are x = 6 or x = -1.
Change a, b or c (whole numbers, a not 0) and the exact solutions follow.
How to work it out
- 1
Write it in standard form a x² + b x + c = 0 and read off the coefficients: a = 2, b = -10, c = -12.
- 2
Work out the discriminant D = b² − 4ac. Its sign tells you how many real solutions there are.
- 3
D is positive, so there are two different real solutions.
- 4
Method 1, factoring. The roots are rational, so the left side factors:
- 5
A product is zero when one of its factors is zero, so set each factor equal to 0 and solve:
- 6
Method 2, The quadratic formula works for every quadratic:
- 7
Simplify to get the solutions:
- 8
Check by putting x = 6 back in: a·x² + b·x + c = 2·(36) + (-10)·(6) + (-12) = 0 ✓
LaTeX source of the formulas on this page
\[ 2x^2 - 10x - 12 = 0\ \Rightarrow\ x = 6,\ -1 \]
\[ 2x^2 - 10x - 12 = 0 \]
\[ D = (-10)^2 - 4\cdot2\cdot(-12) = 100 + 96 = 196 \]
\[ 2\left(x - 6\right)\left(x + 1\right) = 0 \]
\[ x - 6 = 0 \Rightarrow x = 6\qquad x + 1 = 0 \Rightarrow x = -1 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} = \frac{10 \pm \sqrt{196}}{4} \]
\[ x = 6\quad\text{or}\quad x = -1 \]The parabola y = 2x² - 10x - 12
| x | y |
|---|---|
| -0.5 | -6.5 |
| 0.5 | -16.5 |
| 1.5 | -22.5 |
| 2.5 | -24.5 |
| 3.5 | -22.5 |
| 4.5 | -16.5 |
| 5.5 | -6.5 |
Questions
What are the solutions of 2x² - 10x - 12 = 0?
The solutions of 2x² - 10x - 12 = 0 are x = 6 or x = -1.
Does 2x² - 10x - 12 = 0 factor?
Yes: 2(x-6)(x+1) = 0.
What is the vertex of y = 2x² - 10x - 12?
(5/2, -49/2). The parabola opens upwards, so this is the minimum.
What are the sum and product of the roots?
Sum = −b/a = 5, product = c/a = -6.