View Full Version : Linear equations, perpendicular vs parallel lines
Sunshyne05
Sep 23, 2007, 09:16 PM
If you are given two linear equations, how will you say that two lines they represent are parallel or perpendicular to each other.
chris89
Sep 23, 2007, 10:25 PM
A general linear equation is y=mx + c. To determine whether 2 lines are parallel or perpendicular you need to look at the gradient of the equation ( the m bit ).
e.g. y=2x+5, the gradient is 2. if 2 lines are parallel, then their gradients will be identical. If 2 lines are to be perpendicular to each other, then the product( i.e.. What you get when you multiply them together) will be equal to -1.
e.g.. Find a line perpendicular to the line y=2x+5.
The gradient = 2. If m equals gradient of the line we need to find out, then 2*m = -1
m = -1/2. So the line will have equation y= -x/2 + c ( where c can be any number)
terryg752
Oct 9, 2007, 04:49 AM
Put the two equations in the following forms:
y = mx + c
y = nx + d
if m = n then parallel
If mn = -1, perpendicular
temiquel
Oct 30, 2012, 06:44 PM
how would you solve
-10-2x=5y
-5x+2y=-2
to find out whether its parallel, perpendicular, or neither
ebaines
Oct 31, 2012, 06:20 AM
how would you solve
-10-2x=5y
-5x+2y=-2
to find out whether its parallel, perpendicular, or neither
As noted in the earlier posts, put the two equations into the form y = mx+b and compare the values of the m's.