\(\frac{4}{3}.\frac{9}{8}.\frac{16}{15}.....\frac{3481}{3480}\)

\(=\frac{2^2}{1.3}.\frac{3^2}{2.4}.\frac{4^2}{3.5}....\frac{59^2}{58.60}\)

\(=\frac{2.3.4.....59}{1.2.3.....58}.\frac{2.3.4....59}{3.4.5....60}\)

\(=59.\frac{2}{60}=\frac{59}{30}\)

Ta có : \(\frac{4}{3}.\frac{9}{8}.\frac{16}{15}.......\frac{3481}{3480}\)

\(=\frac{2.2}{1.3}.\frac{3.3}{2.4}.\frac{4.4}{3.5}........\frac{59.59}{58.60}\)

\(=\frac{2.3.4........59}{1.2.3.......58}.\frac{2.3.4.......59}{3.4.5........60}\)

\(=59.\frac{1}{30}=\frac{59}{30}\)

A = \(\dfrac{4}{3}\) \(\times\) \(\dfrac{9}{8}\) \(\times\) \(\dfrac{16}{15}\) \(\times\) ....... \(\times\) \(\dfrac{400}{399}\)

Đặt tử số là B; mẫu số là C ta có:

B = 4 \(\times\) 9 \(\times\) 16 \(\times\).....\(\times\) 400

B = 2² \(\times\) 3² \(\times\) 4² \(\times\) ......\(\times\) 20²

B = 2² \(\times\)( 3 \(\times\) 4 \(\times\) .......\(\times\) 19)² \(\times\) 20²

C = 3 \(\times\) 8 \(\times\) 15 \(\times\) ......\(\times\) 339

3      =   1 \(\times\)  3

8      =    2  \(\times\) 4

15    =    3   \(\times\) 5

..........................

399 =   19 \(\times\) 21 

Nhân vế với vết ta được:

C = 1 \(\times\) 2 \(\times\) 3 \(\times\) 4\(\times\)....\(\times\)19\(\times\)3 \(\times\) 4 \(\times\) 5 \(\times\).....\(\times\)21

C = 1 \(\times\) 2 \(\times\)( 3 \(\times\) 4 \(\times\).....\(\times\) 19)² \(\times\) 20 \(\times\) 21

A = \(\dfrac{2^2\times\left(3\times4\times...\times19\right)^2\times20^2}{1\times2\times\left(3\times4\times....\times19\right)^2\times20\times21}\)

A = \(\dfrac{2\times\left(3\times4\times...\times19\right)^2\times20}{2\times\left(3\times4\times...\times19\right)^2\times20}\) \(\times\) \(\dfrac{2\times20}{1\times21}\)

A = 1 \(\times\) \(\dfrac{40}{21}\)

A = \(\dfrac{40}{21}\)

ghi lại đầu bài đi em

A = \(\dfrac{4}{3}\times\dfrac{9}{8}\times\dfrac{16}{15}\times\dfrac{25}{24}\times\dfrac{36}{35}\times\dfrac{49}{48}\times\dfrac{64}{63}\times\dfrac{81}{80}\times\dfrac{100}{99}\times\dfrac{121}{120}\)

A = \(\dfrac{2\times2\times3\times3\times4\times4\times5\times5\times6\times6\times7\times7\times8\times8\times9\times9\times10\times10\times11\times11}{1\times3\times2\times4\times3\times5\times4\times6\times5\times7\times6\times8\times7\times9\times8\times10\times9\times11\times10\times12}\)

A = \(\dfrac{3\times3\times4\times4\times5\times5.....\times10\times10}{3\times3\times4\times4\times5\times5.....\times10\times10}\) \(\times\) \(\dfrac{2\times2\times11\times11}{1\times2\times11\times12}\)

A =1 \(\times\) \(\dfrac{2\times2\times11\times11}{1\times2\times11\times2\times6}\)

A = \(\dfrac{2\times2\times11}{2\times2\times11}\) \(\times\) \(\dfrac{11}{6}\)

A = 1 \(\times\) \(\dfrac{11}{6}\)

A = \(\dfrac{11}{6}\)

= 10150 bạn nhé !

=10150

chúc bạn học giỏi 

hi hi

10150 k mk nhé

\(a)\) \(4.126.25=\left(4.25\right).126=100.126=12600\)

a,4x126x25

=(4x25)x126

=100x126

=12600

cảm ơn 2 bn nhé thank you