State whether the relationship between the variables in the table is a direct variation, an inverse variation, or neither. If it is a direct or inverse variation, write a function to model it.
x=3,9,13,20
y=9,27,39,60

I know it's direct but how do I write a function model to it?

Question

State whether the relationship between the variables in the table is a direct variation, an inverse variation, or neither.  If it is a direct or inverse variation, write a function to model it. 
x=3,9,13,20
y=9,27,39,60

I know it's direct but how do I write a function model to it?

hartnn · Answer

check : if the product xy is constant for all pairs of x,y then the variation is inverse, 
but if the ratio y/x is constant for all pairs of x,y then the variation is direct.

anonymous · Answer

but I don't get how to write a function model to it? :/

hartnn · Answer

so did u get it as inverse or direct ?

anonymous · Answer

direct? it says in my notebook if both x and y increases then it's direct

anonymous · Answer

ooh, do i just put the numbers into the equation y=k/x?

hartnn · Answer

yes, here if you note then, 
y/x = 9/3 = 3
y/x = 27/9 =3
y/x = 39/13 =3 
so , you see everytime the ratio y/x turns out to be = 3
hence your function will also be 
y/x =3 or y =3x.

hartnn · Answer

yes, thats what i did, 
y= kx for direct . 
9=k *3 
---> k=3
so, y=3x :)

anonymous · Answer

I get it now! thank you very much :D xx

hartnn · Answer

welcome ^_^