Can someone explain to me how to do this?

determine whether y varies directly with x. if so, find the constant of variation k and write the equation.

x y
5 20
15 60
45 180
135 540

Question

Can someone explain to me how to do this?

determine whether y varies directly with x. if so, find the constant of variation k and write the equation.

x       y
5       20
15     60
45     180
135   540

cwrw238 · Answer

y = kx   is direct variation  where k is a constant

cwrw238 · Answer

k >= 1


as x increases y will also increase

cwrw238 · Answer

is this the case with your table?

anonymous · Answer

yeah!

cwrw238 · Answer

right  now can you see what k is?

cwrw238 · Answer

5 * k  = 20
15 * k  = 60

do you see the pattern?

anonymous · Answer

yeah

cwrw238 · Answer

k = 20/5 = 4

equation is 
y = 4x

anonymous · Answer

thanks!!