Perpendicular Line

Question

Identify the equation of a line in slope-interecept form that is perpendicular to y = -1/3x + 2 and passes through (2,1).

Answer 1

Hi Faith,

Slope intercept form is y = mx + b

in your equation y = -1/3 x + 2, your slope m is the -1/3 and your b is 2

now to find a slop that is perpendicular you find the negative reciprocal. so -1/3 becomes +3/1 which is 3, we changed the sign from negative to positive and we switched the numerator and denominator. -1/3 to +3/1.

now we have y = 3x + b. Now we use the point (2,1) so x = 2 and y = 1

find b

1 = 3(2) + b

1 = 6 + b

1-6 = b

-5 = b or b = -5

write your equation

y = 3x - 5

Answer 2

y= 3x + b where 3 is the slope and b= y intercept. plug in the point to calculate b. slope is negative inverse of -1/3. change the sign and flip it upside down to get +3/1 = 3

1 = 3(2) + b

b =-5

y=3x - 5 is the perpendicular line through (2,1)