Quadratic Intercepts 25A00B
1. **State the problem:** Find the points where the quadratic graph $y = 5x^2 + 23x + 12$ crosses the $x$-axis and $y$-axis.
2. **Recall the rules:**
- The graph crosses the $x$-axis where $y=0$. So solve $5x^2 + 23x + 12 = 0$.
- The graph crosses the $y$-axis where $x=0$. So find $y$ when $x=0$.
3. **Find the $y$-intercept:**
Substitute $x=0$ into the equation:
$$y = 5(0)^2 + 23(0) + 12 = 12$$
So the $y$-intercept is at $(0, 12)$.
4. **Find the $x$-intercepts:**
Solve the quadratic equation:
$$5x^2 + 23x + 12 = 0$$
Use the quadratic formula:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where $a=5$, $b=23$, $c=12$.
Calculate the discriminant:
$$\Delta = b^2 - 4ac = 23^2 - 4 \times 5 \times 12 = 529 - 240 = 289$$
Calculate the roots:
$$x = \frac{-23 \pm \sqrt{289}}{2 \times 5} = \frac{-23 \pm 17}{10}$$
Two solutions:
- $$x_1 = \frac{-23 + 17}{10} = \frac{-6}{10} = -0.6$$
- $$x_2 = \frac{-23 - 17}{10} = \frac{-40}{10} = -4$$
5. **Write the $x$-intercepts as points:**
- $(-0.6, 0)$
- $(-4, 0)$
**Final answers:**
- $x$-intercepts: $(-0.6, 0)$ and $(-4, 0)$
- $y$-intercept: $(0, 12)$