P = 2/1.3 + 2/3.5 + 2/5.7 + ... + 2/49.51
P = 1 - 1/3 + 1/3 - 1/5 + 1/5 - 1/7 + ... + 1/49 - 1/51
P = 1 - 1/51
P = 50/51
Q = 1/1.3 + 1/3.5 + ... + 1/19.21
Q = 1/2 .(2/1.3 + 2/3.5 + ... + 2/19.21)
Q = 1/2.(1 - 1/3 + 1/3 - 1/5 + ... + 1/19 - 1/21)
Q = 1/2 . (1 - 1/21)
Q = 1/2. 20/21
Q = 10/21
Ủng hộ mk nha ^_-
\(P=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{49.51}\)
\(P=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{49}-\frac{1}{51}\)
\(P=1-\frac{1}{51}\)
\(P=\frac{50}{51}\)
\(Q=\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{19.21}\)
\(Q=\frac{1}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{19.21}\right)\)
\(Q=\frac{1}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{19}-\frac{1}{21}\right)\)
\(Q=\frac{1}{2}.\left(1-\frac{1}{21}\right)\)
\(Q=\frac{1}{2}.\frac{20}{21}\)
\(Q=\frac{10}{21}\)
\(P=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{49.51}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{49}-\frac{1}{51}\)
\(=1-\frac{1}{51}\)
\(=\frac{50}{51}\)
\(Q=\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{19.21}\)
\(2Q=\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{19.21}\)
\(2Q=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{19}-\frac{1}{21}\)
\(2Q=1-\frac{1}{21}\)
\(2Q=\frac{20}{21}\)
\(Q=\frac{20}{21}:2\)
\(Q=\frac{10}{21}\)
