Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
\(A=\dfrac{9}{1.2}+\dfrac{9}{2.3}+\dfrac{9}{3.4}+...+\dfrac{9}{98.99}+\dfrac{9}{99.100}\)
\(A=9-\dfrac{9}{2}+\dfrac{9}{2}-\dfrac{9}{3}+\dfrac{9}{3}-\dfrac{9}{4}+...+\dfrac{9}{99}-\dfrac{9}{100}\)
\(A=9-\dfrac{9}{100}\)
\(A=\dfrac{891}{100}\)
\(A=\dfrac{9}{1.2}+\dfrac{9}{2.3}+\dfrac{9}{3.4}+.......................+\dfrac{9}{98.99}+\dfrac{9}{99.100}\)
\(\Rightarrow A=9\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+.................+\dfrac{1}{98.99}+\dfrac{1}{99.100}\right)\)
\(\Rightarrow A=9\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+..........+\dfrac{1}{98}-\dfrac{1}{99}+\dfrac{1}{99}-\dfrac{1}{100}\right)\)
\(\Rightarrow A=9\left(1-\dfrac{1}{100}\right)\)
\(\Rightarrow A=9.\dfrac{99}{100}\)
\(\Rightarrow A=\dfrac{891}{100}\)
A=9/1.2+9/2.3+9/3.4+.....+9/98.99+9/99.100
=9.(1/1.2+1/2.3+1/3.4+....+1/98.99+1/99.100
=9.(1/1-1/2+1/2-1/3+1/3-1/4+...+1/98-1/99+1/99-1/100)
=9.(1/1-1/100)
=9.99/100
=891/100
CHÚC BẠN HỌC TỐT!
\(A=9.\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\right)\)
\(=9.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(=9.\left(1-\frac{1}{100}\right)\)
\(=9.\frac{99}{100}\)
\(=\frac{891}{100}\)
Giải:
\(A=\dfrac{9}{1.2}+\dfrac{9}{2.3}+\dfrac{9}{3.4}+...+\dfrac{9}{98.99}+\dfrac{9}{99.100}\)
\(\Leftrightarrow A=9\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{98.99}+\dfrac{1}{99.100}\right)\)
\(\Leftrightarrow A=9\left(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{98}-\dfrac{1}{99}+\dfrac{1}{99}-\dfrac{1}{100}\right)\)
\(\Leftrightarrow A=9\left(\dfrac{1}{1}-\dfrac{1}{100}\right)\)
\(\Leftrightarrow A=9.\dfrac{99}{100}\)
\(\Leftrightarrow A=\dfrac{891}{100}\)
Vậy ...
\(\frac{9}{1.2}+\frac{9}{2.3}+\frac{9}{3.4}+...+\frac{9}{99.100}\)
=\(9.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\right)\)
=\(9.\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\right)\)
=\(9.\left(\frac{1}{1}-\frac{1}{100}\right)\)
=\(9.\frac{99}{100}\)
=\(\frac{891}{100}\)
\(A=9\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\right)\)
\(A=9\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(A=9\left(1-\frac{1}{100}\right)\)
\(A=9\times\frac{99}{100}\)
\(A=\frac{891}{100}\) hoặc 8,91
không đăng linh tinh nha bạn