Question

How do you write the direct variation equation if y=42 as x=6, find y for the x-value 3?

Answer 1

`y=7x`
when `x=3` then `y=21`

Explanation:

If `y` varies directly as `x`
`color(white)("XX")color(red)(y)=c*color(blue)(x)` for some constant `c`

We are told
`color(white)("XX")color(red)(42) = c*color(blue)(6)`
`rArrcolor(white)("XX")c=7`

So the equation is
`color(white)("XX")y=7x`

When `x=3`
`color(white)("XX")y=7(3) = 21`