Tính $I = \int {x{{\tan }^2}xdx}$ ta được:

$\int {udv}  = uv + \int {vdu}$

$\int {udv}  = uv - \int {vdu}$          

$\int {udv}  = \int {uv}  - \int {vdu}$

$\int {udv}  = \int {uvdv}  - \int {vdu}$

$\left\{ \begin{array}{l}du = g'\left( x \right)dx\\v = \int {h\left( x \right)dx} \end{array} \right.$

$\left\{ \begin{array}{l}du = g\left( x \right)dx\\v = \int {h\left( x \right)dx} \end{array} \right.$           

$\left\{ \begin{array}{l}du = \int {g\left( x \right)dx} \\v = h\left( x \right)\end{array} \right.$  

$\left\{ \begin{array}{l}du = g'\left( x \right)dx\\v = h\left( x \right)\end{array} \right.$

$I = \left( {x + 1} \right)f\left( x \right) - 2F\left( x \right) + C$     

$I = F\left( x \right) - \left( {x + 1} \right)f\left( x \right)$

$I = \left( {x + 1} \right)f\left( x \right) + C$

$I = \left( {x + 1} \right)f\left( x \right) - F\left( x \right) + C$  

$\int {f(x)dx = {x^3}\ln 3x - \dfrac{{{x^3}}}{3} + C}$        

$\int {f(x)dx = \dfrac{{{x^3}\ln 3x}}{3} - \dfrac{{{x^3}}}{9} + C}$

$\int {f(x)dx = \dfrac{{{x^3}\ln 3x}}{3} - \dfrac{{{x^3}}}{3} + C}$          

$\int {f(x)dx = \dfrac{{{x^3}\ln 3x}}{3} - \dfrac{{{x^3}}}{{27}} + C}$

$\dfrac{1}{4}{x^4}\ln 3x + C$         

$- \dfrac{1}{4}{x^4}\ln 3x - \dfrac{1}{{16}}{x^4} + C$

$- \dfrac{1}{4}{x^4}\ln 3x + \dfrac{1}{{16}}{x^4} + C$

$\dfrac{1}{4}{x^4}\ln 3x - \dfrac{1}{{16}}{x^4} + C$

$a + b = 2$  

$a + b = 3$                

$a + b = 0$     

$a + b = 1$

$- 1$  

$3$

$1$

$2$