Math Is Fun Forum

biljana

Member

Registered: 2008-11-30

Posts: 2

distance between parallel lines

Can you please show me how to find distance between parallel lines whose equations are y=17 and y=-4

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,045

Re: distance between parallel lines

Both the lines y=17 and y =-4 are parallel to the x-axis.
The distance between the origin and y=17 is 17 units and the distance between the origin and y=-4 is 4 units. Hence, the two parallel lines are 21 units apart.

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biljana

Member

Registered: 2008-11-30

Posts: 2

Re: distance between parallel lines

HELP
How I can graph equation y=2/3x-4 and the point (-1,-1).than find x so that the line through (x,2)and (-1,-1)is perperdicular to the graph of y=2/3-4?

careless25

Real Member

Registered: 2008-07-24

Posts: 560

Re: distance between parallel lines

first graph y=2/3x-4
if a line is perpendicular to y=2/3x-4
its slope is the negative reciprocal of the slope of the line y=2/3x-4
negative reciprocal of 2/3 = -3/2
now you know the slope of the perpendicular line
so u get y=-3/2x + b
to solve for b plug in the point (-1,-1)
-1 = -3/2(-1) + b
-5/2=b
perpendicular line : y= -3/2x - 5/2
to solve for x in (x,2) plug it in the perpendicular line equation
2 = -3/2x -5/2
7/2 = -3/2x
-7/3 = x

to graph an equation
y = 2/3x -4
your first point would be (0,-4) because your y-intercept is -4.
then using your slope you either go up 2 and right 3 or down 2 and left 3 to give you (3,-2) and (-3,-6) respectively.

careless25

Real Member

Registered: 2008-07-24

Posts: 560

Re: distance between parallel lines

feel free to ask questions if you need clarification on something!