# M(7, -4) is the midpoint of RS. if S has coordinates (13,5), what are the coordinates of R?

Nov 14, 2015

$R = \left(1 , - 13\right)$

#### Explanation:

Notation: $A = \left({A}_{x} , {A}_{y}\right)$

${M}_{x} = \frac{{R}_{x} + {S}_{x}}{2}$

${M}_{y} = \frac{{R}_{y} + {S}_{y}}{2}$

$7 = \frac{{R}_{x} + 13}{2}$

$- 4 = \frac{{R}_{y} + 5}{2}$

$14 = {R}_{x} + 13$

$- 8 = {R}_{y} + 5$