Question

If y varies inversely as x, how do you find the constant of variation if y = 5 when x = -1?

Answer 1

`y=(-5)/x`

Explanation:

Let `k` be a constant

Write as:`" "y=k/x`

It is given that at `y=5; x=-1`

So by substitution

`" "y=k/x" "->" "5=k/(-1)`

Multiply both sides by `(-1)`

`" "(-1)xx5=(-1)/(-1)xxk`

But `" "(-1)/(-1) = +1`

`" "k=-5`

So the equation is:

`" "y=(-5)/x`