\(\Leftrightarrow\left(\dfrac{x-9}{11}+1\right)+\left(\dfrac{x-10}{12}+1\right)+\left(\dfrac{x-11}{13}+1\right)=\left(\dfrac{x-12}{14}+1\right)+\left(\dfrac{x-28}{15}+2\right)\)

=>x+2=0

=>x=-2

Mk nghĩ là 7,635 nha

8.530555555555556

Làm tròn là 8.5

\(A=\dfrac{6^{12}.3^3.5-7.9^7.2^{13}}{2.4^7.5-2^{14}.3^2}\)

\(=\dfrac{2^{12}.3^{12}.3^3.5-7.3^{14}.2^{12}}{2.2^{14}.5-2^{14}.3^2}\)

\(=\dfrac{2^{12}.3^{15}.5-7.3^{14}.2^{13}}{2.3^{14}.5-2^{14}.3^2}\)

\(=\dfrac{2^{12}.3^{14}.\left(15-14\right)}{2^{14}.\left(2.5-3\right)}\)

\(=\dfrac{3^{14}.1}{2^2}\)

\(=\dfrac{314}{4}\)

\(a,\dfrac{1}{7}+\dfrac{1}{3}=\dfrac{3}{21}+\dfrac{7}{21}=\dfrac{10}{21}\\ b,\dfrac{-2}{3}+\dfrac{-5}{7}=\dfrac{-14+\left(-15\right)}{21}=\dfrac{-29}{21}\\ c,\dfrac{1}{2}-\dfrac{-1}{2}-\dfrac{1}{3}=\dfrac{3+3-2}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)

\(a.\dfrac{4}{28}+\dfrac{12}{36}=\dfrac{1}{7}+\dfrac{1}{3}=\dfrac{3}{21}+\dfrac{7}{21}=\dfrac{10}{21}\\ b.\dfrac{-12}{18}+\dfrac{-15}{21}=\dfrac{-2}{3}+\dfrac{-5}{7}=\dfrac{-14}{21}+\dfrac{-15}{21}=\dfrac{-29}{21}\\ c.\dfrac{14}{28}+\dfrac{16}{32}-\dfrac{17}{51}=\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{17}{51}=1-\dfrac{17}{51}=\dfrac{2}{3}\)

\(\dfrac{4}{28}+\dfrac{12}{36}=\dfrac{144}{1008}+\dfrac{336}{1008}=\\ \dfrac{480}{1008}=\dfrac{10}{21}\)

Câu b và c em làm tương tự.

đây mà là toán lớp 1 à.đồ dở hơi.

ban a toán lớp mấy thì  toán vậy bạn có trả lời được ko mà còn ra vẻ hả bạn 'doraemi'

dúng rồi đó ko trả lời thì thôi 

\(A=\dfrac{6^{12}\cdot3^3\cdot5-7\cdot9^7\cdot2^{13}}{2\cdot4^7\cdot5-2^{14}\cdot3^2}\)

\(=\dfrac{2^{12}\cdot3^{12}\cdot3^3\cdot5-7\cdot3^{14}\cdot2^{13}}{2\cdot2^{14}\cdot5-2^{14}\cdot3^2}\\ =\dfrac{2^{12}\cdot3^{15}\cdot5-7\cdot2^{13}\cdot3^{14}}{2^{15}\cdot5-2^{14}\cdot3^2}\)

\(=\dfrac{2^{12}\cdot3^{14}\left(3\cdot5-7\cdot2\right)}{2^{14}\left(5-3^2\right)}\)

\(=\dfrac{3^{14}\cdot1}{-4}=\dfrac{-3^{14}}{4}=\dfrac{-4782969}{4}=-1195742,25\)

a) https://hoc247.net/hoi-dap/toan-7/thuc-hien-phep-tinh-5-5-27-7-23-0-5-5-27-16-23-faq218258.html

b) https://hoidap247.com/cau-hoi/1507941

b) \(\dfrac{10^9.49^4}{14^8.25^5}=\dfrac{\left(2.5\right)^9.\left(7^2\right)^4}{\left(7.2\right)^8.\left(5^2\right)^5}=\dfrac{2^9.5^9.7^6}{7^8.2^8.5^{10}}=\dfrac{2}{7.7.5}=\dfrac{2}{245}\)

\(a,=\left(\dfrac{140}{27}+\dfrac{1}{2}\cdot\dfrac{5}{27}\right)+\left(\dfrac{7}{23}+\dfrac{16}{23}\right)\\ =\left(\dfrac{140}{27}+\dfrac{5}{54}\right)+1=\dfrac{285}{54}+1=\dfrac{339}{54}=\dfrac{113}{18}\\ b,=\dfrac{2^9\cdot5^9\cdot7^8}{7^8\cdot2^8\cdot5^{10}}=\dfrac{2}{5}\)

\(x:\dfrac{28}{5}=\dfrac{14}{23}\times\dfrac{23}{12}\\ x:\dfrac{28}{5}=\dfrac{7}{6}\\ x=\dfrac{7}{6}\times\dfrac{28}{5}\\ x=\dfrac{98}{15}.\)

X : 28/5 = 14/23 x 23/12

X : 28/5 = 7/6

X = 7/6 x 28/5

X = 98/15

a) số số hạng của dãy số là 

(89-11):1 +1=79

Tổng dãy số là 

(11+89).79:2=3950