Question

Find the equation of the line that passes through (-1, 4) and is perpendicular to the

line that passes through (2, 2) and (4, - 4)
(A) y = 3x + 7
(B) y = - 1/3 x +1/3
(C) y=1/3x+13/3
(D) y =- 3x + 8
(E) none of these

Answer 1

For perpendicular lines, m2 = -1/m1; where m1 is the slope of line 1 and m2 is the slope of line 2.
m1 = (-4 - 2)/(4 - 2) = -6/2 = -3
m2 = -1/-3 = 1/3
Equation of the required line is given by: y - 4 = 1/3 (x - (-1))
y - 4 = 1/3 x + 1/3
y = 1/3 x + 1/3 + 4
y = 1/3 x + 13/3