Answer:
3.5
Step-by-step explanation:
The attached shows the perpendicular bisector to have a slope of m = -1/2 and a y-intercept of b = 4.
m+b = (-1/2) +4 = 3.5
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The difference of coordinates of the two points is ...
B-A = (-5, 4) -(-3, 8) = (-2, -4)
Then the rise/run ratio is (-4)/(-2) = 2. The slope of the perpendicular bisector will have a slope (m) that is the negative reciprocal of this:
m = -1/2
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The average of the coordinates of the two points is ...
(B+A)/2 = ((-5, 4) +(-3, 8))/2 = (-8, 12)/2 = (-4, 6)
Then the point-slope form of the equation of the perpendicular bisector can be written ...
y = (-1/2)(x +4) +6 = (-1/2)x -2 +6
y = (-1/2)x +4
So, the y-intercept is b = 4, and ...
m + b = (-1/2) +4 = 3 1/2
m + b = 3.5