Answer:
4. The equation of the perpendicular bisector is y =  x -
 x -  
 
5. The equation of the perpendicular bisector is y = - 2x + 16
6. The equation of the perpendicular bisector is y =  x +
 x +  
 
Step-by-step explanation:
Lets revise some important rules
- The product of the slopes of the perpendicular lines is -1, that means if the slope of one of them is m, then the slope of the other is  (reciprocal m and change its sign) (reciprocal m and change its sign)
- The perpendicular bisector of a line means another line perpendicular to it and intersect it in its mid-point
- The formula of the slope of a line is   
- The mid point of a segment whose end points are  and and is is  
- The slope-intercept form of the linear equation is y = m x + b, where m is the slope and b is the y-intercept 
4.
∵ The line passes through (7 , 2) and (4 , 6)
- Use the formula of the slope to find its slope
∵  = 7 and
 = 7 and  = 4
 = 4
∵  = 2 and
 = 2 and  = 6
 = 6
∴ 
- Reciprocal it and change its sign to find the slope of the ⊥ line
∴ The slope of the perpendicular line =  
 
- Use the rule of the mid-point to find the mid-point of the line
∴ The mid-point = 
∴ The mid-point = 
- Substitute the value of the slope in the form of the equation
∵ y =  x + b
 x + b
- To find b substitute x and y in the equation by the coordinates 
    of the mid-point
∵ 4 =  ×
 ×  + b
 + b
∴ 4 =  + b
 + b
- Subtract   from both sides
 from both sides
∴  = b
 = b
∴ y =  x -
 x -  
 
∴ The equation of the perpendicular bisector is y =  x -
 x -  
 
5.
∵ The line passes through (8 , 5) and (4 , 3)
- Use the formula of the slope to find its slope
∵  = 8 and
 = 8 and  = 4
 = 4
∵  = 5 and
 = 5 and  = 3
 = 3
∴ 
- Reciprocal it and change its sign to find the slope of the ⊥ line
∴ The slope of the perpendicular line = -2
- Use the rule of the mid-point to find the mid-point of the line
∴ The mid-point = 
∴ The mid-point = 
∴ The mid-point = (6 , 4)
- Substitute the value of the slope in the form of the equation
∵ y = - 2x + b
- To find b substitute x and y in the equation by the coordinates 
    of the mid-point
∵ 4 = -2 × 6 + b
∴ 4 = -12 + b
- Add 12 to both sides
∴ 16 = b
∴ y = - 2x + 16
∴ The equation of the perpendicular bisector is y = - 2x + 16
6.
∵ The line passes through (6 , 1) and (0 , -3)
- Use the formula of the slope to find its slope
∵  = 6 and
 = 6 and  = 0
 = 0
∵  = 1 and
 = 1 and  = -3
 = -3
∴ 
- Reciprocal it and change its sign to find the slope of the ⊥ line
∴ The slope of the perpendicular line = 
- Use the rule of the mid-point to find the mid-point of the line
∴ The mid-point = 
∴ The mid-point = 
∴ The mid-point = (3 , -1)
- Substitute the value of the slope in the form of the equation
∵ y =  x + b
 x + b
- To find b substitute x and y in the equation by the coordinates 
    of the mid-point
∵ -1 =  × 3 + b
 × 3 + b
∴ -1 =  + b
 + b 
- Add   to both sides
  to both sides
∴  = b
 = b
∴ y =  x +
 x +  
 
∴ The equation of the perpendicular bisector is y =  x +
 x + 