( chỉ cần ghi đáp án thoi )câu 1 : Aleft(1-dfrac{1}{2}right)left(1-dfrac{1}{3}right)left(1-dfrac{1}{4}right)....left(1-dfrac{1}{21}right)câu 2 : Bleft(1-dfrac{1}{4}right)left(1-dfrac{1}{9}right)left(1-dfrac{1}{16}right)...left(1-dfrac{1}{100}right)câu 3 : tìm a để dfrac{a}{18}, lớn hơn dfrac{-5}{6}và nhỏ hơn dfrac{-1}{2}câu 4 : Dleft(dfrac{1}{7}right)^0+left(dfrac{1}{7}right)^1+left(dfrac{1}{7}right)^2+....+left(dfrac{1}{7}right)^{2017}câu 5 : E-dfrac{1}{3}+dfrac{1}{3^2}-df...
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( chỉ cần ghi đáp án thoi )
câu 1 : \(A=\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\left(1-\dfrac{1}{4}\right)....\left(1-\dfrac{1}{21}\right)\)
câu 2 : \(B=\left(1-\dfrac{1}{4}\right)\left(1-\dfrac{1}{9}\right)\left(1-\dfrac{1}{16}\right)...\left(1-\dfrac{1}{100}\right)\)
câu 3 : tìm a để \(\dfrac{a}{18}\), lớn hơn \(\dfrac{-5}{6}\)và nhỏ hơn \(\dfrac{-1}{2}\)
câu 4 : \(D=\left(\dfrac{1}{7}\right)^0+\left(\dfrac{1}{7}\right)^1+\left(\dfrac{1}{7}\right)^2+....+\left(\dfrac{1}{7}\right)^{2017}\)
câu 5 : \(E=-\dfrac{1}{3}+\dfrac{1}{3^2}-\dfrac{1}{3^3}+\dfrac{1}{3^4}-.....+\dfrac{1}{3^{50}}-\dfrac{1}{3^{51}}\)
câu 6 : \(F=\dfrac{1}{2}+\dfrac{2}{2^2}+\dfrac{3}{2^3}+\dfrac{4}{2^4}+\dfrac{5}{2^5}+...+\dfrac{100}{2^{100}}\)
câu 7 : rút gọn\(\dfrac{3}{5}+\dfrac{3}{5^4}+\dfrac{3}{5^7}+...+\dfrac{3}{5^{100}}=?\)
câu 8 : tính \(2^2+2^2+2^3+2^4+2^5+....+2^{49}+2^{50}\)
câu 9 : cho A = 1 + 3 +\(3^2+3^3+3^4+...+3^{100}\) khi đó stn 2.A+1=\(3^n\)
