B
btn_hd_1995


anh chị giải thích hộ em 2 chỗ này vs ah!^^
1;
[TEX]\int \frac{ln x . d_( x^2 + 1)}{( x^2 + 1)^2} = \int ln x .d_(\frac{-1}{1 + x^2 })[/TEX]
2;
[TEX]\frac{1}{2}\int x^2.d_(ln( x + \sqrt{1 + x^2}))= \frac{1}{2}\int x^2( 1 + \frac{x}{\sqrt{1 + x^2}})\frac{d_x}{x + \sqrt{1 + x^2}}[/TEX]
1;
[TEX]\int \frac{ln x . d_( x^2 + 1)}{( x^2 + 1)^2} = \int ln x .d_(\frac{-1}{1 + x^2 })[/TEX]
2;
[TEX]\frac{1}{2}\int x^2.d_(ln( x + \sqrt{1 + x^2}))= \frac{1}{2}\int x^2( 1 + \frac{x}{\sqrt{1 + x^2}})\frac{d_x}{x + \sqrt{1 + x^2}}[/TEX]