Question

Which pair of equations represents two perpendicular lines?
(Points : 3)
Option A: -3x +2y = 10 and 3y = 2x +12

Option B: 2x + 5y = 45 and y + 2/5x = -9

Option C: x= 4y +4 and x +4y=4

Option D: 7x + 4y= 20 and y-3=4/7x

Answer 1

if you know the slope of 1 line

slope = m

then the perpendicular line has a slope if

\[slope_{perpendicular} = - \frac{1}{m}\]

so for each option, find the slope of the 1st line,

then get the negative reciprocal and see if its the slope of the 2nd line

Option A -3y + 2y = 10 or y = 3/2 x + 5 slope = 3/2

negative reciprocal is -2/3

2nd line y = 2/3x + 4 slope is 2/3 so not perpendicular...

hope it makes sense

Answer 2

it makes sense im just not sure how to solve to find the slope

Answer 3

so you need the line in slope intercept form

y = mx + b

so just make y the subject in each line

option B has y = -2/5x + 9 and y = -2/5x - 9

same value