Select the correct answer.

Grady's father is building a 15-meter fence with the start of the fence at coordinates \((8,5)\) and the midpoint of the fence at coordinates \((3.5,-1)\). What are the coordinates of the other end of the fence?

A. \((12,6)\)
B. \((-15,-3)\)
C. \((2,-9)\)
D. [tex]\((-1,-7)\)[/tex]



Answer :

To find the coordinates of the other end of the fence, we can use the midpoint formula. The midpoint formula states that if you have a segment with endpoints \((x_1, y_1)\) and \((x_2, y_2)\), the coordinates of the midpoint \(M\) are:
[tex]\[ M = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right) \][/tex]

In this problem, we are given:
- The start point \((x_1, y_1) = (8, 5)\)
- The midpoint \((M_x, M_y) = (3.5, -1)\)

We need to find the coordinates of the other end of the fence \((x_2, y_2)\).

First, we use the x-coordinates to find \(x_2\):
[tex]\[ \frac{8 + x_2}{2} = 3.5 \][/tex]

Multiply both sides by 2 to eliminate the fraction:
[tex]\[ 8 + x_2 = 7 \][/tex]

Then, solve for \(x_2\):
[tex]\[ x_2 = 7 - 8 = -1 \][/tex]

Next, we use the y-coordinates to find \(y_2\):
[tex]\[ \frac{5 + y_2}{2} = -1 \][/tex]

Multiply both sides by 2 to eliminate the fraction:
[tex]\[ 5 + y_2 = -2 \][/tex]

Then, solve for \(y_2\):
[tex]\[ y_2 = -2 - 5 = -7 \][/tex]

Thus, the coordinates of the other end of the fence are \((-1, -7)\).

The correct answer is:
[tex]\[ \boxed{(-1, -7)} \][/tex]