\(A=\frac{11}{21.10^2+10^2}=\frac{11}{10^2.\left(21+1\right)}=\frac{11}{10^2.22}=\frac{11}{10^2.11.2}=\frac{1}{10^2.2}\)

\(B=\frac{3.5.7.11.13.37-10101}{1313130+20202}=\frac{\left(3.5.7.11.13.37\right).5-10101.1}{130.10101+10101.2}=\frac{10101.\left(5-1\right)}{10101.\left(130+2\right)}=\frac{4}{132}=\frac{1}{33}\)

a)\(\frac{7}{1}.\frac{5}{9}.\frac{11}{35}=\frac{7.5.11}{9.5.7}=\frac{11}{9}\)

b) \(\frac{3}{5}.\frac{4}{23}.\frac{5}{6}=\frac{3.2.2.5}{5.23.3.2}=\frac{2}{23}\)

c) \(\frac{5}{2}.\frac{7}{4}.\frac{2}{7}=\frac{5.7.2}{2.7.4}=\frac{5}{4}\)

d)  \(\frac{19}{23}.\frac{12}{17}.\frac{85}{24}=\frac{19.12.5.17}{23.17.12.2}=\frac{19.5}{23.2}=\frac{95}{46}\)

Tính

A. \(\frac{7}{1}x\frac{5}{9}x\frac{11}{35}=\frac{7x5x11}{1x9x35}=\frac{11}{9}\)

B. \(\frac{3}{5}x\frac{4}{23}x\frac{5}{6}=\frac{3x4x5}{5x23x6}=\frac{2}{23}\)

C. \(\frac{5}{2}x\frac{7}{4}x\frac{2}{7}=\frac{5x7x2}{2x4x7}=\frac{35}{28}\)

D. \(\frac{19}{23}x\frac{12}{17}x\frac{85}{24}=\frac{19x12x85}{23x17x24}=\frac{4845}{2346}\)

(2000+8000)+(19999+1)

=10000+2000

=3000

chuc chi hoc tot!

120000

Đặt    \(A=3-3^2+3^3-3^4+....-3^{100}\)

\(\Rightarrow\)\(3A=3^2-3^3+3^4-3^5+.....-3^{101}\)

\(\Rightarrow\)\(A+3A=\left(3-3^2+3^3-3^4+...-3^{100}\right)+\left(3^2-3^3+3^4-3^5+...-3^{101}\right)\)

\(\Rightarrow\)\(4A=3-3^{101}\)

\(\Rightarrow\)\(A=\frac{3-3^{101}}{4}\)

vì tia OC nằm trong góc AOB =>  góc COA+ góc BOC =  góc AOB

                                                         => góc BOC = 135 - 30

                                                               góc BOC = 105 độ

=>  góc BOC là góc tù (>90) 

       góc AOB là góc tù (>90)

      góc COA là  góc nhọn (<90)

tự biết đi

\(3\frac{1}{3}x+16\frac{3}{4}=-13,25\)

\(\frac{10}{3}x+\frac{67}{4}=\frac{-53}{4}\)

\(\frac{10}{3}x=-30\)

\(x=-9\)

\(3\frac{1}{3}x+16\frac{3}{4}=-13,25\)

\(\frac{10}{3}x+\frac{67}{4}=\frac{-53}{4}\)

\(\frac{10}{3}x=-30\)

\(x=-9\)