Explanation:
the slope-intercept form is
y = ax + b
"a" being the slope, "b" being the y-intercept (the y- value when x = 0).
the slope is the ratio (y coordinate difference / x coordinate difference) when going from one point on the line to another.
a perpendicular slope simply turns the original slope upside-down with x and y, and it flips the sign.
the slope of the origins line is 2 = 2/1.
the perpendicular slope is -1/2.
so, the equation looks like
y = -1/2 x + b
to get b we use the point coordinates :
-5 = -1/2 × 2 + b = -1 + b
-4 = b
so, the full equation is
y = -1/2 x - 4