Quotient rule is the straightforward way. Transforming it into a product and then doing product rule gives you exactly your quotient rule formula anyway:
y = f(x) * (g(x))^(-1)
dy/dx = f'(x) * (g(x))^(-1) + f(x) * g'(x) * (-1) * (g(x))^(-2)
dy/dx = f'(x) / g(x) - f(x) * g'(x) / (g(x))^2
Common denominator:
dy/dx = (f'(x) * g(x) - f(x) * g'(x)) / (g(x))^2