Have you seen a mathematician claim that? Because there’s entire algebra they created just so it becomes a fraction.

Brah, chain rule & function composition.

Also multiplying by dx in diffeqs

This is until you do multivariate functions. Then you get for f(x(t), y(t)) this: df/dt = df/dx * dx/dt + df/dy * dy/dt

(d/dx)(x) = 1 = dx/dx

Not very good mathematicians if they tell you they aren’t fractions.