use y=mx+b to find EOL.
if two lines are perpendicular it means their slopes are negative reciprocals of one another. So, if the slope of the given line is 2, the slope of the line we are trying to find is -1/2.
To find “b” (the y-intercept) we have to plug in the given point into y=mx+b with the slope we just found;
y = mx+b
-2 = (-1/2)(-1) + b
-2 = 1/2 + b
-2 - 1/2 = b
-5/2 = b
the EOL is y = -1/2x - 5/2
