Parabolic Intersections
1. **State the problem:** We are given two parabolas based on family birthdates.
Given:
- Father's birth month = 6 (June)
- Father's birth year last two digits = 20
- Mother's birth month = 8 (August)
- Mother's birth year last two digits = 22
The parabolas are:
$$y_1 = -6x^2 + 20$$
$$y_2 = 8x^2 - 22$$
We need to find if they intersect by solving $y_1 = y_2$.
2. **Find intersections by setting $y_1 = y_2$:**
Set:
$$-6x^2 + 20 = 8x^2 - 22$$
Bring all terms to one side:
$$-6x^2 + 20 - 8x^2 + 22 = 0$$
$$(-6x^2 - 8x^2) + (20 + 22) = 0$$
$$-14x^2 + 42 = 0$$
3. **Solve for $x^2$:**
$$-14x^2 = -42$$
$$x^2 = \frac{-42}{-14} = 3$$
4. **Find $x$ values:**
$$x = \pm \sqrt{3}$$
5. **Find corresponding $y$ values by substituting into $y_1$ or $y_2$** (using $y_1$):
$$y = -6(3) + 20 = -18 + 20 = 2$$
So intersections are at:
$$\left(\sqrt{3}, 2\right) \quad \text{and} \quad \left(-\sqrt{3}, 2\right)$$
6. **Since intersection points exist, no need for birthdates from relatives.**
7. **Find the area between the curves:**
The area $A$ between $y_1$ and $y_2$ from $x=-\sqrt{3}$ to $x=\sqrt{3}$ is:
$$A = \int_{-\sqrt{3}}^{\sqrt{3}} |y_1 - y_2| \, dx = \int_{-\sqrt{3}}^{\sqrt{3}} |(-6x^2 + 20) - (8x^2 - 22)| \, dx$$
Simplify inside the integral:
$$(-6x^2 + 20) - (8x^2 - 22) = -6x^2 + 20 - 8x^2 + 22 = -14x^2 + 42$$
Since $-14x^2 + 42 \geq 0$ on the interval, the absolute value can be removed:
$$A = \int_{-\sqrt{3}}^{\sqrt{3}} (-14x^2 + 42) \, dx$$
8. **Calculate the integral:**
$$A = \left[ -14 \frac{x^3}{3} + 42x \right]_{-\sqrt{3}}^{\sqrt{3}} = \left(-\frac{14}{3} x^3 + 42x\right) \Bigg|_{-\sqrt{3}}^{\sqrt{3}}$$
Calculate at upper limit $x=\sqrt{3}$:
$$-\frac{14}{3} (\sqrt{3})^3 + 42 (\sqrt{3}) = -\frac{14}{3} (3 \sqrt{3}) + 42 \sqrt{3} = -14 \sqrt{3} + 42 \sqrt{3} = 28 \sqrt{3}$$
Calculate at lower limit $x=-\sqrt{3}$:
$$-\frac{14}{3} (-\sqrt{3})^3 + 42 (-\sqrt{3}) = -\frac{14}{3} (-3 \sqrt{3}) - 42 \sqrt{3} = 14 \sqrt{3} - 42 \sqrt{3} = -28 \sqrt{3}$$
9. **Subtract:**
$$A = 28 \sqrt{3} - (-28 \sqrt{3}) = 28 \sqrt{3} + 28 \sqrt{3} = 56 \sqrt{3}$$
**Final answer:**
The area between the curves is:
$$56 \sqrt{3}$$