\(A=\frac{2}{2.5}+\frac{2}{5.8}+...+\frac{2}{95.98}\)
\(A=\frac{2}{3}.\left(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{95.98}\right)\)
\(A=\frac{2}{3}.\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{95}-\frac{1}{98}\right)\)
\(A=\frac{2}{3}.\left(\frac{1}{2}-\frac{1}{98}\right)\)
\(A=\frac{2}{3}.\frac{24}{49}\)
\(A=\frac{16}{49}\)
\(A=\frac{2}{2.5}+\frac{2}{5.8}+\frac{2}{8.11}+...+\frac{2}{95.98}\)
\(\Leftrightarrow\frac{3}{2}A=\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+...+\frac{3}{95.98}\)
\(\Leftrightarrow\frac{3}{2}A=\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{95}-\frac{1}{98}\)
\(\Leftrightarrow\frac{3}{2}A=\frac{1}{2}-\frac{1}{98}\)
\(\Leftrightarrow\frac{3}{2}A=\frac{48}{98}=\frac{24}{49}\)
\(\Leftrightarrow A=\frac{24}{49}\div\frac{3}{2}\)
\(\Leftrightarrow A=\frac{48}{147}\)
ko đáp án ko khác bài anh là rút gọn phan số rùi
