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2) $I=\int\dfrac{dx}{\sqrt{3(x-\dfrac{1}{3})(1-x)}}$

Tích phân x/đ với $\dfrac{1}{3}<x<1$

$x=\dfrac{1}{3}+(1-\dfrac{1}{3})sin^2t\to dx=2.\dfrac{2}{3}sint.cost$

Xét $0<t<\dfrac{\pi}{2}\to sint>0,cost>0$

$\sqrt{3(x-\dfrac{1}{3})(1-x)}=\sqrt{3}.\dfrac{2}{3}sint.cost$

$\to I=\int\dfrac{2dt}{\sqrt{3}}=...$
 
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