Question

If y varies directly as x, and y=6 as x=-1, find y for the x-value of 5

Answer 1

`y=-30`

Explanation:

we are given

y varies directly as x

so, we can write equation as

`y=kx`

where

k is constant of proportionality

We have

at x=-1 , y=6

so, we can use it to find k

`6=k(-1)`

so, we get

`k=-6`

now, we can plug it back

`y=-6x`

now, we can plug x=5

and we get

`y=-6* 5`

`y=-30`