Question

What is the y-intercept of the equation of the line that is perpendicular to the line y = 3/5x + 10 and passes through the point (15, –5)?

The equation of the line in slope-intercept form is y = x

Answer 1

y- intercept = 20

y =
`(3)/(5)`x + 10 has slope m =
`(3)/(5)`

The perpendicular slope = -
`(1)/(m)` = -
`(1)/((3)/(5) )` = -
`(5)/(3)`

perpendicular equation is y = -
`(5)/(3)` x + c

where c is the y-intercept

to find c substitute (15 , -5) into the equation

-5 = - 25 + c ⇒ c = - 5 + 25 = 20

y-intercept of perpendicular line is 20