giuóp mik

S

sonsuboy

$\dfrac{5^2}{1.6}+\dfrac{5^2}{6.11}+\dfrac{5^2}{11.16}+\dfrac{5^2}{16.21}+\dfrac{5^2}{21.26}$
=$5.(\dfrac{5}{1.6}+\dfrac{5}{6.11}+\dfrac{5}{11.16}+\dfrac{5}{16.21}+\dfrac{5}{21.25})$
=$5.(\dfrac{1}{1}-\dfrac{1}{6}+\dfrac{1}{6}-....+\dfrac{1}{26}-\dfrac{1}{31})$
=$5.(1-\dfrac{1}{31})$
=$.....$
 
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