Rocket Height 77004A
1. **State the problem:** We want to find the time intervals when the rocket's height $h$ is above 40 meters.
2. **Given model:** The height at time $t$ is given by $$h = -5t^2 + 20t + 25$$
3. **Set up the inequality:** We want to find $t$ such that $$-5t^2 + 20t + 25 > 40$$
4. **Simplify the inequality:** Subtract 40 from both sides:
$$-5t^2 + 20t + 25 - 40 > 0$$
$$-5t^2 + 20t - 15 > 0$$
5. **Divide the inequality by -5:** Remember to reverse the inequality sign when dividing by a negative number:
$$t^2 - 4t + 3 < 0$$
6. **Factor the quadratic:**
$$t^2 - 4t + 3 = (t - 1)(t - 3)$$
7. **Analyze the inequality:**
$$(t - 1)(t - 3) < 0$$ means the product is negative, so $t$ is between the roots:
$$1 < t < 3$$
8. **Interpretation:** The rocket is above 40 meters between 1 second and 3 seconds after launch.
**Final answer:** The rocket is above 40 meters for $$t \in (1, 3)$$ seconds.