Question

Suppose y varies directly with x. write an equation if y=-15 when x=-18.

Answer 1

-15 = k x -18
K x -18 = -15
K= 15/18
Y= 15/18
x X

Answer 2

y =
`(15)/(18)` × x

Explanation:

The standard format of a directly proportional equation goes by the format of

y = k × x

The question asks us to write an equation if y = -15 when x = -18 and y varies directly with x

So we substitute the values y = -15 and x = -18 in the equation y = k × x

K = constant, we have to work this out

-15 = k × -18

k × - 18 = -15

k =
`(15)/(18)`

So then we put this back into the original y = k × x to find our final equation

y =
`(15)/(18)` × x