Step 1: Understanding the Question:
The question asks for the area of the quadrilateral formed by the intersection points of a parabola with the $x$-axis and a horizontal line.
By determining the coordinates of these four points, we can identify the shape of the quadrilateral and calculate its area.
Step 2: Key Formula or Approach:
The intersection points on the $x$-axis are found by setting $y = 0$.
The intersection points with the line $y = 7$ are found by setting $y = 7$.
The area of a trapezoid (since $MN$ and $AB$ are parallel horizontal segments) is given by:
\[ \text{Area} = \frac{1}{2} (a + b) h \]
where $a$ and $b$ are the lengths of the parallel sides, and $h$ is the vertical height.
Step 3: Detailed Explanation:
• First, let us find the coordinates of points A and B where the parabola $y = -x^2 + 16$ intersects the $x$-axis ($y = 0$):
\[ -x^2 + 16 = 0 \implies x^2 = 16 \implies x = \pm 4 \]
Thus, the points are $A(-4, 0)$ and $B(4, 0)$.
The length of the bottom base $AB$ is:
\[ AB = 4 - (-4) = 8 \text{ units} \]
• Next, let us find the coordinates of points M and N where the parabola intersects the line $y = 7$:
\[ -x^2 + 16 = 7 \implies x^2 = 9 \implies x = \pm 3 \]
Thus, the points are $M(-3, 7)$ and $N(3, 7)$.
The length of the top base $MN$ is:
\[ MN = 3 - (-3) = 6 \text{ units} \]
• Since both segments are horizontal, they are parallel to each other.
The quadrilateral $ABNM$ is an isosceles trapezoid.
The vertical height $h$ is the distance between $y = 0$ and $y = 7$, which is:
\[ h = 7 - 0 = 7 \text{ units} \]
• Now, we can calculate the area of the trapezoid:
\[ \text{Area} = \frac{1}{2} (AB + MN) \cdot h \]
\[ \text{Area} = \frac{1}{2} (8 + 6) \cdot 7 = \frac{1}{2} \cdot 14 \cdot 7 = 49 \]
Step 4: Final Answer:
The area of the quadrilateral with vertices A, B, M, and N is 49.