Direct Variation And Locus
1. Problem 6: Given that $y$ varies directly as the square of $(x+1)$, we write the variation as:
$$y = k(x+1)^2$$
where $k$ is the constant of proportionality.
2. Use the given values $y=200$ when $x=4$ to find $k$:
$$200 = k(4+1)^2 = k(5)^2 = 25k$$
So,
$$k = \frac{200}{25} = 8$$
3. Therefore, the equation connecting $y$ and $x$ is:
$$y = 8(x+1)^2$$
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4. Problem 7(a): Construct the locus of point $P$ such that $\angle MPN = 50^\circ$.
- The locus of points $P$ forming a fixed angle $\theta$ with segment $MN$ is an arc of a circle passing through $M$ and $N$.
- Using a ruler and compass, draw the circle segment where $\angle MPN = 50^\circ$.
5. Problem 7(b): Locate point $Q$ such that the area of $\triangle MQN$ is half that of $\triangle MLN$ and $\angle MQN = 50^\circ$.
- Since $\angle MQN = 50^\circ$, point $Q$ lies on the same locus circle from part (a).
- The area of $\triangle MLN$ is given by:
$$\text{Area}_{MLN} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times MN \times 5$$
- To find $Q$ such that $\text{Area}_{MQN} = \frac{1}{2} \text{Area}_{MLN}$, adjust the position of $Q$ on the locus so that the base $MN$ is divided accordingly.
- Use compass and ruler to mark $Q$ on the locus circle satisfying these conditions.
This completes the construction steps for the problem.