Question

Y varies inversely to x. If y= 7 when x= -4, what is y when x=5?

Answer 1

y = -5.6

Explanation:

When x changes by a factor of 5/-4, y changes by a factor that is the inverse of that. (That's what varies inversely means.)

y = (-4/5)(7) = -28/5

y = -5.6

Answer 2

`y = - 5 (3)/(5)`

Explanation:

`y = (k)/(x)`, where k is a constant. (Since y varies inversely to x)

Let's find the value of k first.

when y=7, x= -4,

`7 = (k)/( - 4) \\ k = 7( - 4) \\ k = - 28`

Thus,

`y = ( - 28)/(x)`

When x=5,

`y = ( - 28)/(5) \\ y = - 5 (3)/(5)`