[TEX]\int_{}^{}\frac{\sum_{k=0}^{\frac{1}{2}} C_{\frac{1}{2}}^{k}9^{\frac{1}{2}-k}.x^{2k}}{x^2}dx[/TEX]
[TEX]\int_{}^{}\sum_{k=0}^{\frac{1}{2}} C_{\frac{1}{2}}^{k}9^{\frac{1}{2}-k}.x^{2k-2}dx[/TEx]
[TEX]\frac{\sum_{k=0}^{\frac{1}{2}} C_{\frac{1}{2}}^{k}9^{\frac{1}{2}-k}.x^{2k-1}}{2k-1}+C[/TEX]
ok
cách 2
đặt x= 3tant la ra thôi
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