Solve 5x² - 12x + 7 = 0
The solutions of 5x² - 12x + 7 = 0 are x = 7/5 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 = 5, b = -12, c = 7.
- 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 = 7/5 back in: a·x² + b·x + c = 5·(49/25) + (-12)·(7/5) + 7 = 0 ✓
LaTeX source of the formulas on this page
\[ 5x^2 - 12x + 7 = 0\ \Rightarrow\ x = \frac{7}{5},\ 1 \]
\[ 5x^2 - 12x + 7 = 0 \]
\[ D = (-12)^2 - 4\cdot5\cdot7 = 144 - 140 = 4 \]
\[ \left(5x - 7\right)\left(x - 1\right) = 0 \]
\[ 5x - 7 = 0 \Rightarrow x = \frac{7}{5}\qquad x - 1 = 0 \Rightarrow x = 1 \]
\[ x = \frac{-b \pm \sqrt{D}}{2a} = \frac{12 \pm \sqrt{4}}{10} \]
\[ x = \frac{7}{5}\quad\text{or}\quad x = 1 \]The parabola y = 5x² - 12x + 7
| x | y |
|---|---|
| -1.8 | 44.8 |
| -0.8 | 19.8 |
| 0.2 | 4.8 |
| 1.2 | -0.2 |
| 2.2 | 4.8 |
| 3.2 | 19.8 |
| 4.2 | 44.8 |
Questions
What are the solutions of 5x² - 12x + 7 = 0?
The solutions of 5x² - 12x + 7 = 0 are x = 7/5 or x = 1.
Does 5x² - 12x + 7 = 0 factor?
Yes: (5x-7)(x-1) = 0.
What is the vertex of y = 5x² - 12x + 7?
(6/5, -1/5). The parabola opens upwards, so this is the minimum.
What are the sum and product of the roots?
Sum = −b/a = 12/5, product = c/a = 7/5.