Question

Tính A= \(\frac{9}{4x5}+\frac{9}{5x6}+.....+\frac{9}{35x36}\)

Answer 1

giải chi tiết

Answer 2

\(\frac{9}{4.5}+\frac{9}{5.6}+...+\frac{9}{35.36}\)

\(9.\left(\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{35.36}\right)\)

\(9.\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{35}-\frac{1}{36}\right)\)

\(9.\left(\frac{1}{4}-\frac{1}{36}\right)\)

\(9.\frac{2}{9}\)

\(=2\)

Answer 3

Bằng 2 nhé bạn

Answer 4

\(A=\frac{9}{4x5}+\frac{9}{5x6}+...+\frac{9}{35x36}\)

\(\Rightarrow A=9x\left(\frac{1}{4x5}+\frac{1}{5x6}+...+\frac{1}{35x36}\right)\)

\(\Rightarrow A=9x\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{35}-\frac{1}{36}\right)\)

\(\Rightarrow A=9x\left(\frac{1}{4}-\frac{1}{36}\right)\)

\(\Rightarrow A=9x\frac{2}{9}\)

\(\Rightarrow A=2\)