Question

Y varies directly with x. If y=25 when x=5, find y when x =-4

y =​

Answer 1

y = -20

Explanation:

Given that y varies directly with x it means changing x will also cause change in y

Mathematically it can be written as:

y∝x

Removing the proportionality symbol

y = kx

Given y=25 when x=5 Putting the values

`25 = k(5)\\k = (25)/(5)\\k = 5`

Now

`y = 5x`

We have to find the value of y when x = -4

Putting x=-4

`y = 5(-4)\\y = -20`

Hence,,

y = -20