\(A=\frac{1}{3}.\left(\frac{1}{14}-\frac{1}{17}+\frac{1}{17}-\frac{1}{20}+......+\frac{1}{161}-\frac{1}{164}\right)\)
\(B=\frac{1}{3}.\left(\frac{1}{13}-\frac{1}{19}+.....+\frac{1}{613}-\frac{1}{619}\right)\)
\(A=\frac{1}{3}.\left(\frac{1}{14}-\frac{1}{17}+\frac{1}{17}-\frac{1}{20}+......+\frac{1}{161}-\frac{1}{164}\right)\)
\(B=\frac{1}{3}.\left(\frac{1}{13}-\frac{1}{19}+.....+\frac{1}{613}-\frac{1}{619}\right)\)
so sánh A với 1 , biếtA = \(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+\frac{1}{14.17}+\frac{1}{17.20}\)
\(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+\frac{1}{14.17}+\frac{1}{17.20}\)
Nhanh +Đúng = Tick ( gắp )
\(A=\frac{1}{2.5}\frac{1}{5.8}\frac{1}{8.11}\frac{1}{11.14}\frac{1}{14.17}\frac{1}{17.20}\)
\(B=8400.\left(\frac{1}{1.5}+\frac{1}{5.9}+\frac{1}{9.13}+\frac{1}{13.17}+\frac{1}{17.21}+\frac{1}{21.25}\right)\)
Tính
A= \(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{19.21}\)
B= \(\frac{3}{11.14}+\frac{3}{14.17}+\frac{3}{17.20}+...+\frac{3}{68.71}\)
C= \(\frac{8}{9}.\frac{15}{16}.\frac{24}{25}.\frac{35}{36}.............................\frac{2499}{2500}\)
\(\frac{7x}{2.5}+\frac{7x}{5.8}+\frac{7x}{8.11}+\frac{7x}{11.14}+\frac{7x}{14.17}+\frac{7x}{17.20}=\frac{21}{10}\)
tìm x
1) Tính nhanh:
a) A = \(\frac{3}{2}+\frac{3}{6}+\frac{3}{12}+\frac{3}{20}+....+\frac{3}{90}\)
b) B = \(\frac{2}{2.5}+\frac{2}{5.8}+\frac{2}{8.11}+\frac{2}{11.14}+\frac{2}{14.17}\)
Lưu ý: Dấu chấm là dấu nhân nha mọi người
Áp dụng tính chất: \(\frac{1}{n}.\frac{1}{n+1}=\frac{1}{n}-\frac{1}{n+1}\) để tính:
a) A=\(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{17.20}\)
b) B=\(\frac{5^2}{1.6}+\frac{5^2}{6.11}+...+\frac{5^2}{101.106}\)
NHỚ GHI CÁCH LÀM ĐẦY ĐỦ VÀ CHÍNH XÁC THÌ MÌNH TÍCH CHO!
\(\frac{7x}{2.5}+\frac{7x}{5.8}+\frac{7x}{8.11}+\frac{7x}{11.14}+\frac{7x}{14.17}+\frac{7x}{17.20}=\frac{21}{10}\)tìm x zùm nha nếu không được thì chắc là đề sai đó
Tính:
a)\(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2016}}\)
b)\(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)....\left(1-\frac{1}{20}\right)\)
c)\(\frac{9}{5.8}+\frac{9}{8.11}+\frac{9}{11.14}+\frac{9}{14.17}+...+\frac{9}{2006.2009}\)
( LÀM ĐẦY ĐỦ NHÉ MẤY PẠN! XONG RÙI MÌNH TICK CHO)