The midpoint of AB is M (6,3). If the coordinates of A are (7,4) what are the coordinates of B

Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

Aperpendicular bisector, cd is drawn through point con ab if the coordinates of point a are (-3, 2) and the coordinates of point b are (7,6), the x-intercept of cd is point lies on cd.

The anwser cause i do not understand just plez