View Full Version : need formulae for slope of line

07-15-2004, 06:40 PM
Can someone furnish formulae for calculating slope of a line,relationship between slope of parallel and perpendicular lines?


07-15-2004, 06:50 PM
well for any two points (x1,y1) and (x2,y2) the slope is....


maybe you have heard the old expression rise over run. slope is simply the amount of change in the y-direction divided by the amount of change in the x-direction.

also the relationship between parallel and perpindicular lines is straight forward.

for two lines to be parallel, they must have the same slope. now the general equation for a line is y=mx +b, where m is slope and b is the y-intercept. here is an example of two parallel lines.

y=5x + 6

y=5x - 20

notice the only thing that matters is the m value.

now for a line to perpindicular to another, the slope must be the negative reciprical. that is if one line has slope m, the other line has slope -1/m.

here is an example.

y=5x + 6

y=-1/5x - 8

notice again the only thing that matters the m value.

i hope this helps

07-15-2004, 06:54 PM
If the equation is of the form y = mx + c then slope of the line is m. You can also find slope of any linear line by differentating y with respect to x. That is dy/dx. If you know the end points of any line, suppose (x1, y1) and (x2, y2)then the slope between (x1, y1) and (x2, y2) is (y2 - y1)/(x2 - x1)

Two lines are parallel if their slopes are the same.

Two lines are perpendicular if their slopes are negative reciprocals of each other

07-15-2004, 07:29 PM
thanx a lot guys