Let \(f\) be differentiable on \([1,3]\), with \(f(1)=2\), \(f(3)=4\), and \(\int_{1}³ f(x)\,dx=6\), \(\int_{1}³ x² f(x)\,dx=18\). Evaluate \(\int_{1}³ (x³ - 2 x)f'(x)\,dx\).