a,\(=\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{-4}{9}+\frac{7}{15}\)

\(\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{8}{15}+\frac{7}{15}\right)+\frac{-2}{11}\)

=-1+1+-2/11

=0+-2/11

=-2/11

b,\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{40}\right)+\frac{-5}{17}\)

=1+-1+-5/17

=0+-5/17

=-5/17

c,\(=\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{-2}{9}+-\frac{7}{9}\right)+\frac{16}{17}\)

=1+-1+16/17

=0+16/17

=16/17

d,\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{99}-\frac{1}{101}\)

\(=\frac{1}{3}-\frac{1}{101}=\frac{98}{303}\)

a.\(\frac{-5}{9}\)+\(\frac{8}{15}\)+\(\frac{-2}{11}\)+\(\frac{4}{-9}\)+\(\frac{7}{15}\)

=\(\frac{-5}{9}\)+\(\frac{4}{-9}\)+\(\frac{8}{15}\)+\(\frac{7}{15}\)+\(\frac{-2}{11}\)

=(\(\frac{-5}{9}\)+\(\frac{-4}{9}\))+(\(\frac{8}{15}\)+\(\frac{7}{15}\))+\(\frac{-2}{11}\)

=(-1)+1+\(\frac{-2}{11}\)

=0+\(\frac{-2}{11}\)

=\(\frac{-2}{11}\).

ai tk hộ mk đi

Bài 3:

a) Ta có: \(1.25\cdot\left(-3\frac{3}{8}\right)\)

\(=\frac{5}{4}\cdot\frac{-27}{8}\)

\(=\frac{-135}{32}\)

b) Ta có: \(\frac{-9}{34}\cdot\frac{17}{4}\)

\(=\frac{-9}{4}\cdot\frac{17}{34}\)

\(=-\frac{9}{4}\cdot\frac{1}{2}\)

\(=-\frac{9}{8}\)

c) Ta có: \(-\frac{20}{41}\cdot\frac{-4}{5}\)

\(=\frac{20}{41}\cdot\frac{4}{5}\)

\(=\frac{16}{41}\)

d) Ta có: \(\frac{-6}{7}\cdot\frac{21}{2}\)

\(=-\frac{6}{2}\cdot\frac{21}{7}\)

\(=-3\cdot3=-9\)

Bài 4:

a) Ta có: \(-\frac{5}{2}\cdot\frac{3}{4}\)

\(=-\frac{5\cdot3}{2\cdot4}=\frac{-15}{8}\)

b) Ta có: \(4\frac{1}{5}:\left(-2\frac{4}{5}\right)\)

\(=-\frac{21}{5}:\frac{14}{5}\)

\(=-\frac{21}{5}\cdot\frac{5}{14}\)

\(=-\frac{21}{14}=-\frac{3}{2}\)

c) Ta có: \(1.8:\left(-\frac{3}{4}\right)\)

\(=\frac{9}{5}:\frac{-3}{4}\)

\(=\frac{9}{5}\cdot\frac{4}{-3}\)

\(=-\frac{12}{5}\)

d) Ta có: \(\frac{17}{15}:\frac{4}{3}\)

\(=\frac{17}{15}\cdot\frac{3}{4}\)

\(=\frac{17}{20}\)

p) \(\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{4}{-9}+\frac{7}{15}\)

\(=\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{8}{15}+\frac{7}{15}\right)+\frac{-2}{11}\)

\(=-1+1+\frac{-2}{11}\)

\(=-\frac{2}{11}\)

q) \(\frac{5}{13}+\frac{-5}{17}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)

\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{17}\)

\(=1+\left(-1\right)+\frac{-5}{17}=\frac{-5}{17}\)

r) \(\frac{1}{5}+\frac{-2}{9}+\frac{-7}{9}+\frac{4}{5}+\frac{16}{17}\)

\(=\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{-2}{9}+\frac{-7}{9}\right)+\frac{16}{17}\)

\(=1+\left(-1\right)+\frac{16}{17}=\frac{16}{17}\)

a, Vì 4 < 16 < 64 < 256 (Khi lập TLT luôn lấy số lớn nhất nhân số bé nhất trước rồi mới đến 2 số còn lại)
   Ta có: 256.4 = 1024
              64.16 = 1024
=> 256.4 = 64.16
\(\Rightarrow\frac{256}{64}=\frac{16}{4};\)\(\frac{256}{16}=\frac{64}{4};\)\(\frac{4}{64}=\frac{16}{256};\)\(\frac{4}{16}=\frac{64}{256}\)

\(\text{a)}A=\frac{9}{11}+\frac{5}{7}-\frac{20}{11}+\frac{8}{13}+\frac{2}{7}\)

  \(A=\frac{9}{11}+\frac{5}{7}+\frac{-20}{11}+\frac{8}{13}+\frac{2}{7}\)

  \(A=\left(\frac{9}{11}+\frac{-20}{11}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)+\frac{8}{13}\)

  \(A=\frac{-11}{11}+\frac{7}{7}+\frac{8}{13}\)

  \(A=\left[\left(-1\right)+1\right]+\frac{8}{13}\)

\(A=0+\frac{8}{13}=\frac{8}{13}\)

\(\text{b)}B=\frac{8}{13}+\frac{9}{-17}+\frac{-34}{13}+\frac{-8}{17}\)

   \(B=\left(\frac{8}{13}+\frac{-34}{13}\right)+\left(\frac{-9}{17}+\frac{-8}{17}\right)\)

   \(B=\frac{-26}{13}+\left(-1\right)\)

   \(B=\left(-2\right)+\left(-1\right)=-3\)

\(\text{Hok tốt!}\)

\(\text{@Kaito Kid}\)

A =

B =

C =

C =

C = (4.-12)/(13.17) +

C =

C =

C = 96/221

D = -1/12 - ( 2

D = -1/12 - ( 4

D = -1/12 - (-1

D = -1/12 + 1

-3/36 + 2

D = -1/36

):5/11

E = ):5/11

E = 0:5/11

E = 0

Biết rồi mà đi đố người khác . Chịu chị luôn em lạy 2 tay

tìm n   N để \(\frac{n}{n+1}\) + \(\frac{n}{n+2}\) là số tự nhiên

giúp mik với sắp thi r