Two perpendicular lines have the same x-intercept. An equation of one line is y=3x+1. Determine the equation of the other line.

Question

(1 mark for identifying correct perpendicular slope, 1 mark for substituting correctly and solving for x-intercept, 1 mark for substituting shared point correctly into equation, 1 mark for finding b, 1 mark for creating correct equation of the other line)

Answer 1

Slope of perpendicular line is negative reciprocal to slope of line so -1/3

Set y=0 to find x-intercept so x= -1/3

y = 3(-1/3) +1 = 0

not sure if they want b of given line [b =1] or of perpendicular line [b= - 1/3]

use point slope formula to write equation for perpendicular line using point (0,-1/3)

y- (-1/3) = -1/3[x-0] so y = -1/3x - 1/3