In the standard (x,y) coordinate plane, point M with coordinates (5,4) is the midpoint of AB, and B has coordinates (7,3). What are the coordinates of A ?

1 Answer
Jul 27, 2016

Coordinates of A are (3,5)(3,5)

Explanation:

In a segment if A(x_1,y_1)A(x1,y1) and B(x_2,y_2)B(x2,y2) are coordinates of its end points, the coordinates of midpoint MM are (x_1+x_2)/2,(y_1+y_2)/2x1+x22,y1+y22.

Now we are given A(x_1,y_1)A(x1,y1) and B(7,3)B(7,3), hence midpoint is (x_1+7)/2,(y_1+3)/2x1+72,y1+32, but midpoint is given to be (5,4)(5,4).

Hence (x_1+7)/2=5x1+72=5 i.e. x_1+7=5xx2=10x1+7=5×2=10 and x_1=10-7=3x1=107=3

and (y_1+3)/2=4y1+32=4 i.e. y_1+3=4xx2=8y1+3=4×2=8 and x_1=8-3=5x1=83=5

Hence, coordinates of A are (3,5)(3,5)