Question

M(-1,6) is the midpoint of RS. If S has the coordinates (3,13), find the coordinates of R. Multiple choice:
1) (7,-1)
2) (-5,20)
3) (7,20)
4) (-5,-1)

Answer 1

( Sx + Rx ) / 2 = Mx
(Sy+Ry)/2 = My

Mx = -1
Sx + Rx = -2
Sx = 3
3 +Rx = -2
Rx = -5

My = 6
Sy+Ry = 12
Sy = 13
13 + Ry = 12
Ry = -1

R(-5,-1)

Answer 2

why does Sx + Rx = -2?

Answer 3

Ya i didnt understand that either

Answer 4

(sx + rx) / 2 = Mx
(sx + rx) / 2 = -1

sx+rx = -2

Answer 5

oh ok. i got it. (Sx+Rx)/2 = -1