The formula of a midpoint SR:
[tex]M\left(\dfrac{x_S+x_R}{2},\ \dfrac{y_S+y_R}{2}\right)[/tex]
We have
S(4, 1) and M(7, -5)
Substitute:
[tex]\dfrac{4+x_R}{2}=7\qquad|\cdot2\\\\4+x_R=14\qquad|-4\\\\x_R=10\\\\\dfrac{1+y_R}{2}=-5\qquad|\cdot2\\\\1+y_R=-10\qquad|-1\\\\y_R=-11[/tex]
Answer: R(10, -11)
