các bạn giải gấp giùm mình bai này nhe. thank nhìu luôn

V

vansang02121998

$\dfrac{1}{4}[\dfrac{1}{x(x+2)}-\dfrac{1}{(x+2)(x+4)}]=\dfrac{1}{x(x+2)(x+4)}$

$\Rightarrow \dfrac{1}{2.4.6}+\dfrac{1}{4.6.8}+...+\dfrac{1}{96.98.100}=\dfrac{1}{4}(\dfrac{1}{2.4}-\dfrac{1}{4.6}+\dfrac{1}{4.6}-\dfrac{1}{6.8}+...+\dfrac{1}{96.98}-\dfrac{1}{98.100}=\dfrac{1}{4}(\dfrac{1}{2.4}-\dfrac{1}{98.100})=\dfrac{153}{4900}$
 
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