Question

How do you write the direct variation equation if y=-4 when x=2, find y when x=-6?

Answer 1

`y=-2x`
When `x=-6` then `y=12`

Explanation:

If `y` and `x` are in direct variation then
`color(white)("XXX")y=c*x` for some constant `c`

We are told
`color(white)("XXX")-4=c2`
`color(white)("XXX")rarr c=-2`
So `y=-2x`

when `x=-6` this becomes
`color(white)("XXX")y=(-2)*(-6)`
`color(white)("X")rarr y=12`