Question

The midpoint of PQ is M=2,−1 One endpoint is
P=7,6. Find the coordinates of the other endpoint, Q.

Answer 1

let the other endpoint be (a,b)
recall how to find the midpoint:
for the x-coordinate, add up the x's of the endpoints , then divide by 2
for the y-coordinate, add up the y's of the endpoints , then divide by 2

so for the x of the endpoint:
(a+7)/2 = 2
a+7 = 4
a = -3

find b in the same way.

check if your answer is reasonable by making a sketch