Question

[Nhimsinkkdeppp10]

3/1.4+3/4.7+3/7.10+3/10.13+3/13.6

Answer 1

[★彡✿ทợท彡★]

\(\dfrac{3}{1\cdot4}+\dfrac{3}{4\cdot7}+\dfrac{3}{7\cdot10}+\dfrac{3}{10\cdot13}+\dfrac{3}{13\cdot16}\)

\(=\dfrac{3\cdot1}{1\cdot4}+\dfrac{3\cdot1}{4\cdot7}+\dfrac{3\cdot1}{7\cdot10}+\dfrac{3\cdot1}{10\cdot13}+\dfrac{3\cdot3}{13\cdot16}\)

\(=3\cdot\left(\dfrac{1}{1\cdot4}+\dfrac{1}{4\cdot7}+\dfrac{1}{7\cdot10}+\dfrac{1}{10\cdot13}+\dfrac{1}{13\cdot16}\right)\)

\(=3\cdot\left(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{16}\right)\)

\(=3\cdot\left(1-\dfrac{1}{16}\right)\)

\(=3\cdot\left(\dfrac{16}{16}-\dfrac{1}{16}\right)\)

\(=3\cdot\dfrac{15}{16}\)

\(=\dfrac{45}{16}\)

Answer 2

[libichancute]

ngu :3