Answer:
m = -1
Explanation:
Find the equation in slope intercept form [ y = mx + b ] for line AB. Find the slope using the formula [ y2-y1/x2-x1 ].
8-5/7-4
3/3
1
Find the y-intercept.
5 = 1(4) + b
5 = 4 + b
1 = b
So the equation of the line AB is y = x + 1.
The slope of a perpendicular line is the opposite reciprocal of the original line.
1 -> -1/1 -> -1
Best of Luck!