Write an appropriate direct variation equation if y = 27 when x = 9
Write an appropriate inverse variation equation if y = 2 when x = 9
If y varies directly as x, and y = 15 as x = -3, find y for the x-value of 4.
If y varies inversely as x, and y = 5 as x = 6, find y for the x-value of 10.

Question

Write an appropriate direct variation equation if y = 27 when x = 9
Write an appropriate inverse variation equation if y = 2 when x = 9
If y varies directly as x, and y = 15 as x = -3, find y for the x-value of 4.
If y varies inversely as x, and y = 5 as x = 6, find y for the x-value of 10.

loser66 · Answer

Where are you stuck?

sloppycanada · Answer

The first two, I think I can take a stab at the second two since I did similar problems earlier, I just need someone to look the things over.

loser66 · Answer

y = kx =27
and x =9, then k =?

sloppycanada · Answer

k = 3?

loser66 · Answer

yup, hence the required equation is y = 3x. Dat sit.

sloppycanada · Answer

Okay so, for the other one, it's the opposite. 

y = xk?

loser66 · Answer

hey, xk = kx

sloppycanada · Answer

oh yeah... okay..

x = yk?

loser66 · Answer

same!! because yk = x , then y = (1/k)x , that is one of the form y = nx where n = 1/k.

sloppycanada · Answer

Oh yeah the curved graph with two lines is the inverse. And those equations are 1/x... so in our case.?