Đặt \(t=\sqrt{2x-1}\Rightarrow t^2=2x-1\Rightarrow 2tdt=2dx\Rightarrow dx=tdt\) Khi x = 1 thì t =1; khi x = 5 thì t = 3 Do đó \(I=\int_{1}^{3}\frac{tdt}{t+5}=\int_{1}^{3}\frac{(t+5-5)dt}{t+5}=\int_{1}^{3}dt-5\int_{1}^{3} \frac{dt}{t+5}\) \(=\int_{1}^{3}dt-5\int_{1}^{3}\frac{d(t+5)}{t+5}\) \(=t\bigg|^3_1-5ln\left | t+5 \right |\bigg|^3_1=2-5(ln8-ln6)=2-5ln\frac{4}{3}\)