\(x(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{132}=\) \(5\frac{1}{2}\)        

 \(x\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{11\cdot12}\right)=\frac{11}{2}\)

 \(x\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{11}-\frac{1}{12}\right)=\frac{11}{2}\)

 \(x\left(1-\frac{1}{12}\right)=\frac{11}{2}\)

 \(x\cdot\frac{11}{12}=\frac{11}{2}\)

 \(x=\frac{11}{2}:\frac{11}{12}\)

\(x=6\)

Vậy x = 6

\(\frac{x}{2}+\frac{x}{6}+\frac{x}{12}+\frac{x}{20}+...+\frac{x}{132}=5\frac{1}{2}\)

\(\Rightarrow x\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{132}\right)=\frac{11}{2}\)

\(\Rightarrow x\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{11.12}\right)=\frac{11}{2}\)

\(\Rightarrow x\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{11}-\frac{1}{12}=\frac{11}{2}\right)\)

\(\Rightarrow x\left(1-\frac{1}{12}\right)=\frac{11}{2}\)

\(\Rightarrow x.\frac{11}{12}=\frac{11}{12}\)

\(\Rightarrow x=\frac{11}{12}:\frac{11}{12}=1\)

Vậy x = 1

Kết quả là: \(\frac{81}{182}\)

Kết quả : 81

            _____

            182

a) X=6,Y=7

b) X=6

bạn có thể ghi bài này chi tiết hơn cho mình được không ?

\(\Rightarrow\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{6}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)

\(\Rightarrow\frac{1}{3}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)

\(\Rightarrow\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}-\frac{1}{3}\)

\(\Rightarrow\frac{1}{42}\cdot\frac{x}{3}=\frac{-2}{21}\)

\(\Rightarrow\frac{x}{3}=\frac{-2}{21}\div\frac{1}{42}\)

\(\Rightarrow\frac{x}{3}=-4\)

\(\Rightarrow\frac{x}{3}=\frac{-12}{3}\)

\(\Rightarrow x=-12\)

=4

Chính xác 100%.k cho mình nha bạn!!Chúc bạn học tốt!!!

\(\frac{20}{16}\)+\(\frac{3}{15}\)+\(\frac{2}{12}\)+\(\frac{3}{4}\)+\(\frac{4}{5}\)+\(\frac{5}{6}\)= (\(\frac{20}{16}\)+\(\frac{3}{4}\) )+( \(\frac{3}{15}\)+ \(\frac{4}{5}\) )+( \(\frac{2}{12}\)+ \(\frac{5}{6}\) )

                                                                  = 2+1+1 = 4

Chúc bạn học tốt !!!

\(a=\frac12+\frac56+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}\)

\(=1-\frac12+1-\frac16+1-\frac{1}{12}+1-\frac{1}{20}+1-\frac{1}{30}+1-\frac{1}{42}+1-\frac{1}{56}\)

\(=7-\left(\frac12+\frac16+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}\right)\)

\(=7-\left(1-\frac12+\frac12-\frac13+\frac13-\frac14+\frac14-\frac15+\frac15-\frac16+\frac16-\frac17+\frac17-\frac18\right)\)

\(=7-\left(1-\frac18\right)=7-\frac78=\frac{56}{8}-\frac78=\frac{49}{8}\)

Đề bài:
a = 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56

Giải:
Ta thấy mỗi phân số có tử số = mẫu số trừ 1
Vậy ta viết lại:

a = (2 - 1)/2 + (6 - 1)/6 + (12 - 1)/12 + (20 - 1)/20 + (30 - 1)/30 + (42 - 1)/42 + (56 - 1)/56
= 1 - 1/2 + 1 - 1/6 + 1 - 1/12 + 1 - 1/20 + 1 - 1/30 + 1 - 1/42 + 1 - 1/56
= 7 - (1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56)
= 7 - 3/2
= 11/2

Đáp số: 11/2

\(\frac{5}{1.6}\)+ \(\frac{5}{6.11}\)+ .........+\(\frac{5}{501.506}\)

=\(\frac{1}{1.6}+\frac{1}{6.11}+.....+\frac{1}{501.506}\)

=\(\frac{1}{1}-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+......+\frac{1}{501}-\frac{1}{506}\)

=\(\frac{1}{1}-\frac{1}{506}\)

= tự tính nha

Giải

Làm thử thoi nhoa !

a)8,3.39-2,93.500+19,8.20

=323,7-1465+396

=323,7+396-1465

=719,7-1456

=-745,3