Tính:
a, \(\dfrac{2}{1.3}\)+\(\dfrac{2}{3.5}\)+\(\dfrac{2}{2019.2021}\)
b, \(\dfrac{3}{2}\)+\(\dfrac{3}{2^2}\)+\(\dfrac{3}{2^3}\)+-...+\(\dfrac{3}{2^{2018}}\)
tk cho bạn nhanh nhất❤
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