\(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}\)

\(=\frac{2-1}{1\times2}+\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}+\frac{6-5}{5\times6}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)

\(=1-\frac{1}{6}=\frac{5}{6}\)

mình ko viết lại đầu bài nhé

= 1 - 1/2    +      1/2 -1/3     + 1/3 - 1/4  + 1/4 - 1/5 + 1/5 - 1/6 

= 1 - 1/6 = 5/6

trong phép tính đầu mỗi số hạng mk tách làm 1 hiệu nhé

\(2\times5\times\dfrac{11}{3}\times11\times5=\left(2\times5\times5\right)\times\left(\dfrac{11}{3}\times11\right)=50\times\dfrac{121}{3}=\dfrac{6050}{3}\)

2 x 5 x 11/3 x 11 x 5 

= 10 x 11/3 x 11 x 5

=   ( 10 x 5 ) x( 11/3 x 11)

=  50             x  121/3

= 6050/3

2 x 5 x 11/3 x 11 x 5 

= 10 x 11/3 x 11 x 5

=   ( 10 x 5 ) x( 11/3 x 11)

=  50             x  121/3

= 6050/3

(2+4+6+8+...+100) x (15x3-15x2-15)

=(2+4+6+8+....+100)x(15x(3-2-1))

=(2+4+6+8+...+100)x(15x0)

=(2+4+6+8+...+100)x0

=0

Giúpppp mìnhh vớiiiiiiiiiiiiiiiiiiiiiiiii nhanhhhhhhhhhhh lênnnnnnnnnnnnnnnnn

Nhanh rồi mình tích cho

a: \(\dfrac{6}{7}\cdot\dfrac{16}{15}\cdot\dfrac{7}{6}\cdot\dfrac{21}{32}=\dfrac{16}{32}\cdot\dfrac{21}{15}=\dfrac{1}{2}\cdot\dfrac{7}{5}=\dfrac{7}{10}\)

b: \(\dfrac{21}{17}\cdot\dfrac{13}{14}\cdot56\cdot\dfrac{3}{42}=\dfrac{21}{14}\cdot\dfrac{13}{17}\cdot\dfrac{1}{14}\cdot56=\dfrac{78}{17}\)

c: \(=\dfrac{11}{21}\left(\dfrac{7}{4}+\dfrac{5}{4}\right)=\dfrac{11}{21}\cdot3=\dfrac{11}{7}\)

bạn ghi + - x : nhá

muốn biết thì tra goolge bằng 260/100