a) Đặt \(u = 2x - 1\), \(v = x + 2\). Khi đó \(u' = 2\), \(v' = 1\).
\[y' = \frac{u'v - uv'}{v^2} = \frac{2(x+2) - (2x-1) \cdot 1}{(x+2)^2}\]
\[= \frac{2x + 4 - 2x + 1}{(x+2)^2} = \frac{5}{(x+2)^2}\]
b) Đặt \(u = 2x\), \(v = x^2 + 1\). Khi đó \(u' = 2\), \(v' = 2x\).
\[y' = \frac{u'v - uv'}{v^2} = \frac{2(x^2+1) - 2x \cdot 2x}{(x^2+1)^2}\]
\[= \frac{2x^2 + 2 - 4x^2}{(x^2+1)^2} = \frac{-2x^2 + 2}{(x^2+1)^2}\]