Question

Given that y varies directly with x, use the values specified to write a

direct variation equation relating y to x.

x = -19, y = 190


Use your answer to find x when y = -9.

Answer 1

(a)y=-10x

(b)x=0.9

Explanation:

If y varies directly with x, we write:

`y \propto x\\y=kx$ where k is the constant of proportionality.\\If $x = -19, y = 190\\190=-19k\\$Divide both sides by -19\\k=190 / -19\\k=-10\\`

Therefore, a direct variation equation relating y to x is:

(a)y=-10x

(b)When y=-9

Substituting y=-9 into the equation obtained in (a) above

`-9=-10x\\$Divide both sides by -10$\\x=-9/ -10\\x=0.9\\$Therefore, when $ y=-9, x=0.9`