Question

Is this equation `-12x = 6y` a direct variation and if so, what is the constant?

Answer 1

Yes, it represents a direct variation because variables `x` and `y` have constant ratio.

To demonstrate this, divide both sides of an equation by the same number `6`. This is an invariant transformation into an equivalent equation
`y=-2x`
from which follows that the constant of variation equals
`k=-2`.