\(\frac{20}{69}\)

\(\frac{4}{3x7}\)+ \(\frac{5}{7x12}\)+ \(\frac{1}{12x13}\)+ \(\frac{7}{13x20}\)+ \(\frac{3}{20x23}\)

= \(\frac{4}{3}+5\)+\(1+7+\frac{3}{13}\)

=\(4+5+1+7+\frac{1}{13}\)

=\(17+\frac{1}{13}\)

=\(\frac{17}{1}+\frac{1}{13}=\frac{221+1}{13}=\frac{222}{13}\)

\(=\frac{3}{4}\left(\frac{1}{5.9}+\frac{1}{9.13}+...+\frac{1}{41.45}\right)\)

\(=\frac{3}{4}\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+...+\frac{1}{41}-\frac{1}{45}\right)\)

\(=\frac{3}{4}\left(\frac{1}{5}-\frac{1}{45}\right)\)

\(=\frac{3}{4}\times\frac{8}{45}\)

\(=\frac{2}{15}\)

giải giùm đi

\(A=\frac{3}{5\cdot9}+\frac{3}{9\cdot13}+\frac{3}{13\cdot17}+...+\frac{3}{37\cdot41}+\frac{3}{41\cdot45}\)

\(\frac{4A}{3}=\frac{9-5}{5\cdot9}+\frac{13-9}{9\cdot13}+\frac{17-13}{13\cdot17}+...+\frac{41-37}{37\cdot41}+\frac{45-41}{41\cdot45}\)

\(\frac{4A}{3}=\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{37}-\frac{1}{41}+\frac{1}{45}-\frac{1}{45}\)

\(\frac{4A}{3}=\frac{1}{5}-\frac{1}{45}=\frac{9-1}{45}=\frac{8}{45}\Rightarrow A=\frac{8}{45}\cdot\frac{3}{4}=\frac{2}{15}\)

\(a,\)\(x+\frac{4}{5.9}+\frac{4}{9.13}+\frac{4}{13.17}+...+\frac{4}{41.45}=-\frac{37}{45}\)

  \(x+\left(\frac{9-5}{5.9}+\frac{13-9}{9.13}+\frac{17-13}{13.17}+...+\frac{45-41}{41.45}\right)=-\frac{37}{45}\)

  \(x+\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+\frac{1}{13}-\frac{1}{17}+....+\frac{1}{41}-\frac{1}{45}\right)-\frac{37}{45}\)

 \(x+\left(\frac{1}{5}-\frac{1}{45}\right)=-\frac{37}{45}\)

 \(x+\frac{8}{45}=-\frac{37}{45}\)

\(x=-\frac{37}{45}-\frac{8}{45}\)

\(x=-1\)

thế phần b, c đâu bạn

sửa lại : \(\frac{37\cdot13-3}{24+37\cdot12}\)

Đặt \(A=\frac{9+\frac{9}{11}+\frac{18}{23}-\frac{27}{37}}{8+\frac{8}{11}+\frac{16}{23}-\frac{24}{37}}-\frac{2+\frac{16}{29}-\frac{24}{13}-\frac{32}{11}}{3+\frac{24}{29}-\frac{36}{13}-\frac{48}{11}}\)\(=\frac{9\left(1+\frac{1}{11}+\frac{2}{23}-\frac{3}{37}\right)}{8\left(1+\frac{1}{11}+\frac{2}{23}-\frac{3}{37}\right)}-\frac{2\left(1+\frac{8}{29}-\frac{12}{13}-\frac{16}{11}\right)}{3\left(1+\frac{8}{29}-\frac{12}{13}-\frac{16}{11}\right)}\)

\(=\frac{9}{8}-\frac{2}{3}\)(do \(1+\frac{1}{11}+\frac{2}{23}-\frac{3}{37};1+\frac{8}{29}-\frac{12}{13}-\frac{16}{11}\ne0\))

\(=\frac{27}{24}-\frac{16}{24}=\frac{11}{24}.\)

Vậy A = \(\frac{11}{24}.\)

11x12x13 = 1716

11x12x13=1716

ai tích cho mk thì mk kích lại

11x12x13=1716

tíck mik nha

11 x 12 x 13 x14 = 24024.

11x12x13x14=24024

ai k cho mk thì mk k lại cho kích mau ko hết nha

11 x 12 x 13 x 14 = 24024 

k rùi đó

\(\frac{37.13-13}{24+37.12}\)

\(=\frac{37.12+37-13}{24+37.12}=\frac{37.12+24}{24+37.12}=1\)

#

(37.13-13)/(24+37.12)

= 1

#

Ta có \(37.13-13=37.\left(12+1\right)-13\)

\(=37.12+37-13\)

\(=37.12+24\)

Do đó \(\frac{37.13-13}{24+37.12}=\frac{37.12+24}{37.12+24}\)

nên số dư sẽ là 0

Đối với bài này bạn làm nhân trong ngoặc trước -> làm phép cộng trừ còn lại rồi bỏ ngoặc làm phép chia nhé

   ( 37 . 13 - 13 ) : ( 24 + 37 . 12 )

= ( 481 - 13 ) : ( 24 + 444 )

= 468 : 468

=1

k mik nhé

  (37.13-13) : (24+37.12)

=(481-13) : (24+444)

=468:468

=1

Đáp án là 1

HOK TỐT