Question

I said no it's not a function but why isn't it a function?

Answer 1

Because -2x Can't have two values, this also applies for -1x, these are tricky though because y can have any number of x values, but x can only have one y value.

Answer 2

It will only be a function if every x-value only has one y-value.

When x=0, there are y-values at both 6 and 10.

When x=-1, there are y-values at both 4 and 12.

When x=-2, there are y-values at both 2 and 14.

This graphs a sideways parabola, which is not a function because there are multiple y-values for every x-value that isn't zero.