Find the direct variation equation of the graph through the points (0, 0) and (1, -2). Write in y=kx form. (Points : 1)
y = 2x
y = -2x
y = 1/2 x
y = -1/2 x

Question

Find the direct variation equation of the graph through the points (0, 0) and (1, -2). Write in y=kx form. (Points : 1)  
       y = 2x
       y = -2x
       y = 1/2 x
       y = -1/2 x

surry99 · Answer

what have you tried so far?

blondey_315 · Answer

nothing so far i'm still not sure how to do it could you help?

surry99 · Answer

sure..how do you calculate the slope of a line if you have any two points on the line?

surry99 · Answer

There is an equation for it...

blondey_315 · Answer

hmm is it y2*x2 or somthing like that?

surry99 · Answer

slope = (y2-y1)/(x2-x1)...can you now calculate the slope of the line?

anonymous · Answer

www.youtube.com/watch?v=JXRN_LkCa_o

blondey_315 · Answer

hang on im doin it~

blondey_315 · Answer

eh doubt i got i t right but i got 0...

surry99 · Answer

ok...(0,0)   is x1, y1
       (1, -2) is x2, y2   (BTW you can reverse the selection of points, it makes no difference

so slope = (y2 - y1)/(x2-x1) = (-2 -0)/(1-0) = -2

do you agree?

blondey_315 · Answer

ooohhhhhh~ i see!

surry99 · Answer

now from y = kx   k is the slope you just calculated...

surry99 · Answer

so the answer is.....?

blondey_315 · Answer

so B? or y=-2x

surry99 · Answer

yes...does that make sense to you know?

blondey_315 · Answer

Yea i was looking at the equation wrong thank you for the help!

surry99 · Answer

you are welcome...any time