

tính nhanh :
a, 1/3 + 1/15 + 1/35 + 1/63 +...+1/675 + 1/783
b, 1/9 + 1/18 + 1/36 + 1/72 + 1/144 + 1/288 + 1/376 + 1/752
@besttoanvatlyzxz
a, 1/3 + 1/15 + 1/35 + 1/63 +...+1/675 + 1/783
b, 1/9 + 1/18 + 1/36 + 1/72 + 1/144 + 1/288 + 1/376 + 1/752
@besttoanvatlyzxz
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