Question

Is this correct?
functions

Answer 1

yep because the function is f(x) = 0.15x which is in the form y = mx+b (general slope intercept form for a linear equation)

Answer 2

I think a quadratic function makes more sense
refer to series formula :
\[S_n = \dfrac{n}{2}\left[2a+(n-1)d\right] = \mathcal{O}(n^2)\]

Answer 3

Thanks