Chắc là đề bài viết nhầm đó em
[laTEX]\int \frac{dx}{\sqrt{1+x^2}} = ln (x + \sqrt{1+x^2}) + C \\ \\ I = \int_{0}^{1}\sqrt{x^2+1}dx \\ \\ u = \sqrt{x^2+1} \Rightarrow du = \frac{x}{\sqrt{x^2+1}} \\ \\ dv = dx \Rightarrow v = x \\ \\ I = x\sqrt{x^2+1} \big|_0^1 - \int_{0}^{1}\frac{(x^2+1-1)dx}{\sqrt{x^2+1}} \\ \\ I = x\sqrt{x^2+1} \big|_0^1 - \int_{0}^{1}\sqrt{x^2+1}dx + \int_{0}^{1}\frac{dx}{\sqrt{x^2+1}} \\ \\ I = x\sqrt{x^2+1} \big|_0^1 - I + ln(x + \sqrt{1+x^2}) \big|_0^1 \\ \\ I = \frac{1}{2}(x\sqrt{x^2+1} + ln(x + \sqrt{1+x^2}) ) \big|_0^1[/laTEX]