Question

tính bằng các các thuận tiền nhất : A = 1/30 + 1/42 + 1/56 =....+1/600

Answer 1

\(A=\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+...+\dfrac{1}{600}\)

\(A=\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}+...+\dfrac{1}{24\times25}\)

\(A=\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+...+\dfrac{1}{24}-\dfrac{1}{25}\)

\(A=\dfrac{1}{5}-\dfrac{1}{25}\)

\(A=\dfrac{5}{25}-\dfrac{1}{25}\)

\(A=\dfrac{4}{25}\)

\(#WendyDang\)

Answer 2

A = 1/5x6 + 1/6x7 + 1/7x8 + .... + 1/24x25

A = 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8 + ... + 1/24 - 1/25

A = 1/5 - 1/25

A = 4/25

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