a lớn hơn hay sao ý

B lớn hơn A nha bạn 

k cho mk nha bạn

9: \(=1-\dfrac{1}{99}+1-\dfrac{1}{100}+\dfrac{100}{101}\cdot\dfrac{1-4+3}{12}=2-\dfrac{199}{9900}=\dfrac{19601}{9900}\)

10: \(=\left(\dfrac{78}{79}+\dfrac{79}{80}+\dfrac{80}{81}\right)\cdot\dfrac{6+5+9-20}{30}=0\)

a)\(\dfrac{3}{10}\)-x=\(\dfrac{25}{30}\)-\(\dfrac{4}{30}\)

\(\dfrac{3}{10}-x=\dfrac{7}{10}\)

x = \(\dfrac{3}{10}-\dfrac{7}{10}\)

x=\(\dfrac{-4}{10}\)

b)\(\dfrac{-5}{8}+x=\dfrac{4}{9}-\dfrac{63}{9}\)

\(\dfrac{-5}{9}+x=\dfrac{-59}{9}\)

\(x=\dfrac{-59}{9}-\dfrac{-5}{9}\)

\(x=\dfrac{-64}{9}\)

c)=>2.18=(x-3).(x-3)

=>36=(x-3)\(^2\)

=>6\(^2\)=(x-3)\(^2\)

6= x-3

x=6+3=9

Ta có: \(A=\left(\dfrac{1}{3}-1\right)\left(\dfrac{1}{6}-1\right)\left(\dfrac{1}{10}-1\right)\left(\dfrac{1}{15}-1\right)\left(\dfrac{1}{21}-1\right)\left(\dfrac{1}{28}-1\right)\left(\dfrac{1}{36}-1\right)\)

\(=\dfrac{-2}{3}.\dfrac{-5}{6}.\dfrac{-9}{10}.\dfrac{-14}{15}.\dfrac{-20}{21}.\dfrac{-27}{28}.\dfrac{-35}{36}\)

\(=\dfrac{-2.\left(-5\right).3.\left(-3\right).2.\left(-7\right).\left(-4\right).5.\left(-3\right).9.5.\left(-7\right)}{3.2.3.2.5.3.5.3.7.4.7.4.9}\)

\(=\dfrac{-5}{3.4}=\dfrac{-5}{12}\)

Vậy \(A=\dfrac{-5}{12}.\)

\(C=1+\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2016}}\)

\(2C=2\left(1+\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2016}}\right)\)

\(2C=2+1+\dfrac{1}{2}+\dfrac{1}{2^2}+....+\dfrac{1}{2^{2015}}\)

\(2C-C=\left(2+1+\dfrac{1}{2}+...+\dfrac{1}{2^{2015}}\right)-\left(1+\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{2016}}\right)\)

\(C=2-\dfrac{1}{2^{2016}}\)

A= 33.(\(\dfrac{1}{3}.\dfrac{3}{5}.\dfrac{5}{7}.....\dfrac{97}{99}\))

A=33.\(\left(\dfrac{1.3.5.....97}{3.5.7.....99}\right)=33.\dfrac{1}{99}=\dfrac{33.1}{99}=\dfrac{33}{99}=\dfrac{1}{3}\)

Vậy A = \(\dfrac{1}{3}\)

chuc thi tot