= -2 nha bn :))

Hok tốt !

Bài làm

Gọi số cần tìm là x. 

Ta có:  \(-\frac{8}{6}< \frac{ }{2}< -\frac{3}{6}\)

\(-\frac{8}{6}=-\frac{16}{12}\)

\(-\frac{3}{6}=-\frac{6}{12}\)

Mà -16 < x < -6

=>  x = -15, -14, -13, -12, -11, -10, -9, -8, -7.

Vậy x = -15, -14, -13, -12, -11, -10, -9, -8, -7.

# Chúc bạn học tốt #

\(\frac{-8}{6}< \frac{-2}{2}< \frac{-3}{6}\)

#Học Tốt#

\(\left(\frac{3}{4}-\frac{13}{11}+\frac{7}{5}\right)-\left(3-\frac{1}{2}-\frac{35}{11}\right)+\left(\frac{11}{4}-\frac{2}{5}\right)\)

= \(\frac{3}{4}-\frac{13}{11}+\frac{7}{5}-3+\frac{1}{2}+\frac{35}{11}+\frac{11}{4}-\frac{2}{5}\)

= \(\left(\frac{3}{4}+\frac{11}{4}+\frac{1}{2}\right)\left(-\frac{13}{11}+\frac{35}{11}\right)+\left(\frac{7}{5}-\frac{2}{5}\right)-3\)

= \(8+2+1-3\)

= \(8\)

#)Giải :

\(\left(\frac{3}{4}-\frac{13}{11}+\frac{7}{5}\right)-\left(3-\frac{1}{2}-\frac{35}{11}\right)+\left(\frac{11}{4}-\frac{2}{5}\right)\)

\(=\frac{3}{4}-\frac{13}{11}+\frac{7}{5}-3+\frac{1}{2}+\frac{35}{11}+\frac{11}{4}-\frac{2}{5}\)

\(=\left(\frac{3}{4}+\frac{11}{4}\right)+\left(-\frac{13}{11}+\frac{35}{11}\right)+\left(\frac{7}{5}-\frac{2}{5}\right)-3+\frac{1}{2}\)

\(=\frac{7}{2}+2+1-3+\frac{1}{2}\)

\(=\frac{7}{2}+\frac{1}{2}\)

\(=4\)

\(\left(\frac{3}{4}-\frac{13}{11}+\frac{7}{5}\right)-\left(3-\frac{1}{2}-\frac{35}{11}\right)+\left(\frac{11}{4}-\frac{2}{5}\right)\)

\(=\frac{3}{4}-\frac{13}{11}+\frac{7}{5}-3+\frac{1}{2}+\frac{35}{11}+\frac{11}{4}-\frac{2}{5}\)

\(=\left(\frac{3}{4}+\frac{11}{4}\right)+\left(-\frac{13}{11}+\frac{35}{11}\right)+\left(\frac{7}{5}-\frac{2}{5}\right)-3+\frac{1}{2}\)

\(=\frac{7}{2}+2+1-3+\frac{1}{2}\)

\(=\left(\frac{7}{2}+\frac{1}{2}\right)+2+1-3\)

\(=4+2+1-3\)

\(=4\)

Chỉ có một \(\frac{3}{8}\)thôi nha

\(C=\frac{2}{4.7}-\frac{3}{5.9}+\frac{2}{7.10}-\frac{3}{9.13}+...+\frac{2}{301.304}-\frac{3}{401.405}\)

\(C=\left(\frac{2}{4.7}+\frac{2}{7.10}+...+\frac{2}{301.304}\right)-\left(\frac{3}{5.9}+\frac{3}{9.13}+...+\frac{3}{401.405}\right)\)

\(C=\frac{2}{3}\left(\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{301.304}\right)-\frac{3}{4}\left(\frac{4}{5.9}+\frac{4}{9.13}+...+\frac{4}{401.405}\right)\)

\(C=\frac{2}{3}\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{301}-\frac{1}{304}\right)-\frac{3}{4}\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+..+\frac{1}{401}-\frac{1}{405}\right)\) \(C=\frac{2}{3}\left(\frac{1}{4}-\frac{1}{304}\right)-\frac{3}{4}\left(\frac{1}{5}-\frac{1}{405}\right)\)

\(C=\frac{25}{152}-\frac{4}{27}\)

\(C=\frac{67}{4104}\)

ra 67/1014

67/4104

Giải:

Ta có:

\(\frac{x}{2}=\frac{y}{3};\frac{y}{2}=\frac{z}{5}\)

\(\Rightarrow\frac{x}{4}=\frac{y}{6};\frac{y}{6}=\frac{z}{15}\)

\(\Rightarrow\frac{x}{4}=\frac{y}{6}=\frac{z}{15}\)

Theo tính chất dãy tỉ số bằng nhau, ta có:

\(\frac{x}{4}=\frac{y}{6}=\frac{z}{15}=\frac{x+y+z}{4+6+15}=\frac{50}{25}=2\)

+) \(\frac{x}{4}=2\Rightarrow x=8\)

+) \(\frac{y}{6}=2\Rightarrow y=12\)

+) \(\frac{z}{15}=2\Rightarrow z=30\)

Vậy x = 8

       y = 12

       z = 30

\(\frac{x}{2}=\frac{y}{3};\frac{y}{2}=\frac{z}{5}\) và x + y + z =50

\(\frac{x}{4}=\frac{y}{6};\frac{y}{6}=\frac{z}{15}\)
\(\Rightarrow\frac{x}{4}=\frac{y}{6}=\frac{z}{15}\)

Áp dụng dãy tỉ số bằng nhau ta có :

\(\frac{x}{4}+\frac{y}{6}+\frac{z}{15}=\frac{50}{25}=2\)

=> x = 2.4 = 8

=> y = 2.6 = 12

=> z = 2.15 = 30

Vậy x = 8;y = 12;z = 30. 

\(\frac{x}{2}=\frac{y}{3}\Rightarrow\frac{x}{4}=\frac{y}{6}\) và \(\frac{y}{2}=\frac{z}{5}\Rightarrow\frac{y}{6}=\frac{z}{15}\)

\(\Rightarrow\frac{x}{4}=\frac{y}{6}=\frac{z}{15}\)

Áp dụng tc dãy tỉ = nhau 

\(\frac{x}{4}=\frac{y}{6}=\frac{z}{15}=\frac{x+y+z}{4+6+15}=\frac{50}{25}=2\)