Question

which of the following is the equation of a line that passes through (-2,-1) and (-4,-3)?
y=1/2x + 1, y=x + 1, y =1/2x - 1, or y = x - 1

Answer 1

Hello, lets first look at what the slop must be. We know to have a slope, we must have at least 2 points, and they must lie on a straight line. Lets call these two points P1, and P2.

Answer 2

The formula for slope is \[m = \frac{y2-y1}{x2-x1}\]

Answer 3

So in this case, point P1 has coordinates (x1,y1) = (-2,-1) and point P2 has coordinates (x2,y2)=(-4,-3)

Answer 4

Plugging those into the slope you get (-3-(-1))/(-4-(-2)) = m = 1

Answer 5

so it is either choice b or choice d

Answer 6

to find out which, we must use the point-slope form of the line \[m = (y-y1)/(x-x1) or y = m(x-x1) + y1\]

Answer 7

oooh my!

Answer 8

yeah that came out like crap

Answer 9

its y=m(x-x1) + y1

Answer 10

now we have m, y1, and x1

Answer 11

what's m?

Answer 12

the slope

Answer 13

which is 1 in this case, using the two points we are given

Answer 14

ugh im just trying to prepare for this Pert test! trying to make sure i understand EVERYTHING

Answer 15

ahh, answer should be y =x -1

Answer 16

Show me why

Answer 17

So we have 2 points, (-2,-1) and (-4,-3), do you know how to find slope given 2 points?

Answer 18

I think so.. I kind of remember that

Answer 19

so if you graph the two points, and connect a line its (rise)/(run) so how far do i have to go in the y direction divided by how far i have to go in the x direction between the two points

Answer 20

in the y direction I go from (-3 to -1) total distance

Answer 21

and in the x direction i go from -4 to -2

Answer 22

or sorry, i had that backwards
in the y direction we go from -1 to -3 and from -2 to -4 in x

Answer 23

:(

Answer 24

lol, ok let me graph something real quick