Question

Consider the line y=-8/5x+6.

Find the equation of the line that is parallel to this line and passes through the point (5, 3).
Find the equation of the line that is perpendicular to this line and passes through the point (5, 3).
Note that the ALEKS graphing calculator may be helpful in checking your answer.
Equation of parallel line:
Equation of perpendicular line:

Answer 1

Explanation:

the equation

y = -8/5 x + 6

tells us 2 things :

-8/5 is the slope of the line, 6 is the y-intercept (the y value when x = 0).

a parallel line has the same slope (just a different y-intercept) : -8/5

a perpendicular line (intercepts at 90°) turns the original slope upside-down and flips the sign : 5/8

we the use the given point as x and y values and calculate the y-intercepts.

parallel :

3 = -8/5 × 5 + y-intercept = -8 + y-intercept

11 = y-intercept

y = -8/5 x + 11

perpendicular :

3 = 5/8 × 5 + y-intercept = 25/8 + y-intercept

(3×8)/8 = 24/8 = 25/8 + y-intercept

-1/8 = y-interceot

y = 5/8 x - 1/8 = 1/8 × (5x - 1)