2\(\dfrac{1}{3}\)=\(\dfrac{7}{3}\).
chúc bạn học tốt!
\(2\dfrac{1}{3}=2+\dfrac{1}{3}=\dfrac{6}{3}+\dfrac{1}{3}=\dfrac{7}{3}\)
\(2\dfrac{1}{3}=\dfrac{2\cdot3+1}{3}=\dfrac{7}{3}\)
2\(\dfrac{1}{3}\)=\(\dfrac{7}{3}\).
chúc bạn học tốt!
\(2\dfrac{1}{3}=2+\dfrac{1}{3}=\dfrac{6}{3}+\dfrac{1}{3}=\dfrac{7}{3}\)
\(2\dfrac{1}{3}=\dfrac{2\cdot3+1}{3}=\dfrac{7}{3}\)
1) Tìm x biết:
\(\left(1-\dfrac{3}{10}-x\right):\left(\dfrac{19}{10}-1-\dfrac{2}{5}\right)+\dfrac{4}{5}=1\)
2) Tính nhanh
a)\(\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}+\dfrac{1}{3.4.5}+...+\dfrac{1}{10.11.12}\)
b)\(\dfrac{1^2}{1.2}.\dfrac{2^2}{2.3}.\dfrac{3^2}{3.4}.\dfrac{4^2}{4.5}\)
[ 1+2\(\dfrac{1}{3}\)-3\(\dfrac{1}{4}\)]:[1+3\(\dfrac{7}{12}\)-4\(\dfrac{1}{2}\)]
tính
1 .Tìm x biết
a. ( \(\dfrac{1}{1.4}+\dfrac{1}{4.7}+\dfrac{1}{7.10}+...+\dfrac{1}{97.100}\)) = \(\dfrac{0,33x}{2009}\)
b. 1 + \(\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{10}+...+\dfrac{2}{x\left(x+1\right)}=1\dfrac{1991}{1993}\)
c. \(\dfrac{1}{2013}x+1+\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{2012.2013}=2\)
d. 2x + \(\dfrac{7}{6}+\dfrac{13}{12}+\dfrac{21}{20}+\dfrac{31}{30}+\dfrac{43}{42}+\dfrac{57}{56}+\dfrac{73}{72}+\dfrac{91}{90}=10\)
2. Chứng minh rằng :
a. \(\dfrac{1}{4}+\dfrac{1}{4^2}+\dfrac{1}{4^3}+...+\dfrac{1}{4^{99}}< \dfrac{1}{3}\)
b. \(\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}+...+\dfrac{1}{18.19.20}< \dfrac{1}{4}\)
câu 1: tìm x biết: ( \(\dfrac{3}{4.5}\) +\(\dfrac{3}{5.6}\)+\(\dfrac{3}{6.7}\)+\(\dfrac{3}{7.8}\)+\(\dfrac{3}{8.9}\)+\(\dfrac{3}{9.10}\)) . x =\(\dfrac{9}{2}\)
1.
a, \(^{^2}\left(x-2\right)=9\) b,\(^{^3}\left(3x-1\right)=-8\) c, \(\left(x+\dfrac{1}{2}\right)^2=\dfrac{1}{16}\) d, \(\left(\dfrac{2}{3}\right)^x=\dfrac{4}{9}\) e, \(\left(\dfrac{1}{2}\right)^{x-1}=\dfrac{1}{16}\) f,\(\left(\dfrac{1}{2}\right)^{2x-1}=8\)
2.tìm số tự nhiên n biết
a, \(3^{n-1}=27\) b, \(3^{n-1}=\dfrac{1}{243}\) c, \(\left(\dfrac{1}{2}\right)^{2n-1}=\dfrac{1}{8}\) d, \(\left(-\dfrac{1}{3}\right)^{n-5}=\dfrac{1}{81}\) e,\(2^{-1}.2^n+4.2^n=9.2^5\)
tính
G= \(\dfrac{1}{2}\)+ \(\dfrac{1}{2^2}\)+\(\dfrac{1}{2^3}\)+...+\(\dfrac{1}{2^5}\)
Q=\(\dfrac{1}{2}\)+\(\dfrac{1}{2^2}\)+\(\dfrac{1}{2^3}\)+...+ \(\dfrac{1}{2^{10}}\)
m.n giúp e vs nhé\! trình bày rõ ràng nha^^ cảm ơn nhiều ạ <3
Tính nhanh :
F=\(\dfrac{2}{6}\)+\(\dfrac{2}{12}+...+\dfrac{2}{240}\)
G= \(\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+\dfrac{1}{81}+\dfrac{1}{243}\)
H= \(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+...+\dfrac{1}{1024}\)
tính nhanh
C=[\(^{\dfrac{17}{28}}\)+\(\dfrac{18}{29}\)-\(\dfrac{19}{30}\)-\(\dfrac{20}{11}\)].[\(\dfrac{1}{2}\)-\(\dfrac{1}{3}\)-\(\dfrac{1}{6}\)]
Câu 1: Tính nhanh: a/ \(\dfrac{3}{11x12}\)+\(\dfrac{3}{12x13}\)+\(\dfrac{3}{13x14}\)+\(\dfrac{3}{14x15}\)
b/\(\dfrac{2}{2X3}\)+\(\dfrac{2}{3x4}\)+\(\dfrac{2}{4x5}\)+\(\dfrac{2}{5x6}\)
c/ \(\dfrac{3}{1x4}\)+\(\dfrac{3}{4x7}\)+\(\dfrac{3}{7x10}\)+................+\(\dfrac{3}{97x100}\)
d/ \(\dfrac{3}{2x5}\)+\(\dfrac{3}{5x8}\)+\(\dfrac{3}{8x11}\)+.............+\(\dfrac{3}{100x103}\)
e/ \(\dfrac{1}{1x5}\)+\(\dfrac{1}{5x10}\)+\(\dfrac{1}{10x15}\)+..................+\(\dfrac{1}{95x100}\)
Toán lớp 5 nha, giúp với mai mình học r, đúng mk tick cho.
Tính ( bằng cách thuận tiên nếu có thể )
a, A = \(\dfrac{3^2}{10}\)+\(\dfrac{3^2}{40}\)+\(\dfrac{3^2}{8^8}\)+...+\(\dfrac{3^2}{340}\)
b, A = \(\dfrac{5^2}{1\cdot6}\)+\(\dfrac{5^2}{6\cdot11}\)+...+\(\dfrac{5^2}{26\cdot31}\)
c, A = \(\dfrac{1}{2}\)+\(\dfrac{2}{2\cdot4}\)+\(\dfrac{3}{4\cdot7}\)+\(\dfrac{4}{7\cdot11}\)+\(\dfrac{5}{11\cdot16}\)
d, A = \(\dfrac{3}{54}+\dfrac{5}{126}+\dfrac{7}{249}+\dfrac{8}{609}\)
e, A = \(\dfrac{2}{3}+\dfrac{14}{15}+\dfrac{34}{35}+\dfrac{62}{63}\)