=> -A = \(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{95.97}-\frac{1}{97.99}\)
=> -2A = \(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{95.97}-\frac{2}{97.99}\)
=> \(-2A=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{95}-\frac{1}{97}-\frac{1}{97}+\frac{1}{99}\)
=> \(-2A=1-\frac{1}{97}-\frac{1}{97}+\frac{1}{99}=\frac{9502}{9603}\)
=> \(A=\frac{9502}{9603}:\left(-2\right)=-\frac{4751}{9603}\)
Tính: A = 1/99.97- 1/97.95- 1/95.93- ..... -1/5.3- 1/3.1
1/(99.97)-1/(97.95)-1/(95.93)-...-1/(5.3)-1/(3.1). Tính nhanh
Tinh:A=1/99.97-1/97.95-1/95.93-...-1/5.3-1/3.1
Tính hợp lí:
A=\(\frac{1}{299.297}\)- \(\frac{1}{297.295}\) - \(\frac{1}{295.293}\)-...-\(\frac{1}{3.1}\)
1:Tính
a, 7+6.(\(-\frac{1}{2}\))\(^2\)
b, \(\frac{2^5.7+2^5}{2^5.5^2-2^5.3}\)
a, A=\(\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
Chứng tỏ rằng:
a)\(\frac{3}{5.2!}+\frac{3}{5.3!}+\frac{3}{5.4!}+...+\frac{3}{5.100!}< \frac{3}{5}\)
b) \(\frac{1}{2!}+\frac{1}{3!}+\frac{1}{4!}+..+\frac{1}{100!}< 1\)
P/S: dấu ! nghĩa là dấu dư thừa. Vd: n! = 1x2x3x.......x n
Tính tổng: S = \(\frac{1}{2011.2009}\)- \(\frac{1}{2009.2007}\)- ....... - \(\frac{1}{3.1}\)
Thu gọn
\(B=\frac{2^3-3^4-2^4.3^3}{2^5.3^4-2^6.3^3}\)
\(C=\frac{\frac{1}{2}-\frac{1}{2}:\frac{3}{4}-\frac{3}{4}}{\frac{2}{3}-\frac{2}{3}:\frac{5}{6}-\frac{5}{6}}\)
Tinh tong
A=\(\frac{1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{97}}{\frac{1}{1.99}+\frac{1}{3.97}+\frac{1}{97.3}+\frac{1}{99.1}}\)
