M(5, 7) is the midpoint of RS. The coordinates of S are (6, 9). What are the coordinates of R?

A. (10, 14)
B. (5.5, 8)
C. (4, 5)
D. (7, 11)



Answer :

To find the coordinates of point [tex]\( R \)[/tex], given that point [tex]\( M(5, 7) \)[/tex] is the midpoint of segment [tex]\( \overline{RS} \)[/tex] and point [tex]\( S \)[/tex] has coordinates [tex]\( (6, 9) \)[/tex], we can use the properties of midpoints.

The midpoint [tex]\( M \)[/tex] of a segment with endpoints [tex]\( R(x_1, y_1) \)[/tex] and [tex]\( S(x_2, y_2) \)[/tex] is calculated as follows:
[tex]\[ M_x = \frac{R_x + S_x}{2} \][/tex]
[tex]\[ M_y = \frac{R_y + S_y}{2} \][/tex]

Given:
[tex]\[ M_x = 5, \quad M_y = 7 \][/tex]
[tex]\[ S_x = 6, \quad S_y = 9 \][/tex]

We need to find the coordinates [tex]\( (R_x, R_y) \)[/tex] of point [tex]\( R \)[/tex].

1. For the x-coordinate:
[tex]\[ 5 = \frac{R_x + 6}{2} \][/tex]
To isolate [tex]\( R_x \)[/tex], multiply both sides by 2:
[tex]\[ 10 = R_x + 6 \][/tex]
Then, subtract 6 from both sides:
[tex]\[ R_x = 4 \][/tex]

2. For the y-coordinate:
[tex]\[ 7 = \frac{R_y + 9}{2} \][/tex]
To isolate [tex]\( R_y \)[/tex], multiply both sides by 2:
[tex]\[ 14 = R_y + 9 \][/tex]
Then, subtract 9 from both sides:
[tex]\[ R_y = 5 \][/tex]

Thus, the coordinates of [tex]\( R \)[/tex] are [tex]\( (4, 5) \)[/tex].

Therefore, the correct answer is:
[tex]\[ \boxed{(4, 5)} \][/tex]