A=1-1/2+1/2-1/3+1/3-1/4
A=1-1/4=3/4
ai k mk mk k lại
A = 1 - 1/2 + 1/2 - 1/3 - 1/4
A = 1 - 1/4 = 3/4
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
ai trả lời nhanh nhất và đúng nhất sẽ đc tick^-^!!!!!!!!!!!!!!!!!!!!!!!
Chứng tỏ rằng:\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{99.100}< 1\)
Ai nhanh nhất sẽ đc tick
Tính A: 1.2 + 2.3 + 3.4 + .. + 99.100
TÍNH A-B BIẾT
a=1.2+2.3+3.4+4.5+....+98.99
b=12+22+32+....+982
S=\(\frac{1}{1.2}\)+\(\frac{1}{2.3}\)+\(\frac{1}{3.4}\)..........+\(\frac{2006}{2007}\)
chơi vui 1 lúc nào mọi người ơi!!!
1.2+2.3+1+1+1=?????
Tính
A=\(\frac{1}{1.2}x\frac{1}{2.3}x...x\frac{1}{9.10}\)
Tính
\(\frac{1}{2.3}+\frac{1}{3.4}+.........+\frac{1}{99.100}\)
e,\(A=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+\left(1-\frac{1}{20}\right)+\left(1-\frac{1}{20}\right)+\left(1-\frac{1}{42}\right)\)
\(\Rightarrow A=1-\frac{1}{2}+1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+1-\frac{1}{30}+1-\frac{1}{42}=4-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\right)\)
\(\Rightarrow A=4-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\right)=4-\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\right)\)
\(\Rightarrow A=4-\left(\frac{1}{1}-\frac{1}{7}\right)=4-\frac{6}{7}=3\frac{1}{7}\)
