Use the given endpoint Y and the midpoint M of YZ (there is a line over YZ) to find the coordinates of the other endpoint Z
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The x-coordinate of our midpoint = 3
The x-coordinate of Y = 0
k = x-coordinate of Z
3 = (0 + k) / 2
Multiply both sides by 2
6 = k + 0
Simplify
6 = k
The y-coordinate of our midpoint = 3
the y-coordinate of Y = 5
w = y-coordinate of Z
3 = (w + 5) / 2
Multiply both sides by 2
6 = w + 5
Subtract 5 from both sides
1 = w
For problem #17, Z(6, 1)
Let's do problem 18 now.
The x-coordinate of our midpoint = 5
The x-coordinate of Y = -1
k = x-coordinate of Z
5 = (k + (-1)) / 2
Multiply both sides by 2
10 = k + (-1)
Simplify the right side
10 = k - 1
Add 1 to both sides
11 = k
The y-coordinate of our midpoint = 9
The y-coordinate of Y = -3
w = y-coordinate of Z
9 = (w + (-3)) / 2
Multiply both sides by 2
18 = w + (-3)
Simplify the right side
18 = w - 3
Add 3 to both sides
21 = w
For problem #18, Z(11, 21)