a: \(\dfrac{7}{2}-1,5+\dfrac{-8}{11}=3,5-1,5-\dfrac{8}{11}=2-\dfrac{8}{11}=\dfrac{22-8}{11}=\dfrac{14}{11}\)

b: \(\left(1\dfrac{3}{7}+3\dfrac{4}{7}\right):\dfrac{6}{5}-2,5\cdot\dfrac{8}{15}\)

\(=\left(1+\dfrac{3}{7}+3+\dfrac{4}{7}\right)\cdot\dfrac{5}{6}-\dfrac{5}{2}\cdot\dfrac{8}{15}\)

\(=5\cdot\dfrac{5}{6}-\dfrac{40}{30}=\dfrac{25}{6}-\dfrac{4}{3}=\dfrac{17}{6}\)

c: \(\dfrac{7}{9}\cdot\dfrac{35}{17}-\dfrac{7}{9}\cdot\dfrac{25}{17}-\dfrac{7}{9}\)

\(=\dfrac{7}{9}\left(\dfrac{35}{17}-\dfrac{25}{17}-1\right)\)

\(=\dfrac{7}{9}\cdot\dfrac{-7}{17}=\dfrac{-49}{117}\)

d: \(\left(120\%+1\dfrac{3}{5}\right):\dfrac{27}{5}-4,5\cdot\dfrac{4}{9}\)

\(=\left(1,2+1,6\right)\cdot\dfrac{5}{27}-2\)

\(=\dfrac{14}{27}-2=\dfrac{14}{27}-\dfrac{54}{27}=-\dfrac{40}{27}\)

e: \(\dfrac{-5}{7}\cdot x=\dfrac{25}{12}\)

=>\(x=-\dfrac{25}{12}:\dfrac{5}{7}=-\dfrac{25}{12}\cdot\dfrac{7}{5}=\dfrac{-5\cdot7}{12}=-\dfrac{35}{12}\)

g: \(\dfrac{7}{11}+\dfrac{1}{11}\cdot x=0,3-3\dfrac{2}{5}\)

=>\(\dfrac{x}{11}=0,3-3,4-\dfrac{7}{11}=-\dfrac{411}{110}\)

=>\(x=-\dfrac{411}{110}\cdot11=-\dfrac{411}{10}\)

hơi dài đó.

a: \(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{x\left(x+1\right)}=\dfrac{2021}{2022}\)

=>\(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{x}-\dfrac{1}{x+1}=\dfrac{2021}{2022}\)

=>\(1-\dfrac{1}{x+1}=\dfrac{2021}{2022}\)

=>\(\dfrac{1}{x+1}=1-\dfrac{2021}{2022}=\dfrac{1}{2022}\)

=>x+1=2022

=>x=2021

b: Sửa đề: \(\dfrac{x+1}{99}+\dfrac{x+2}{98}+\dfrac{x+3}{97}+\dfrac{x+4}{96}=-4\)

=>\(\left(\dfrac{x+1}{99}+1\right)+\left(\dfrac{x+2}{98}+1\right)+\left(\dfrac{x+3}{97}+1\right)+\left(\dfrac{x+4}{96}+1\right)=0\)

=>\(\dfrac{x+100}{99}+\dfrac{x+100}{98}+\dfrac{x+100}{97}+\dfrac{x+100}{96}=0\)

=>\(\left(x+100\right)\left(\dfrac{1}{99}+\dfrac{1}{98}+\dfrac{1}{97}+\dfrac{1}{96}\right)=0\)

=>x+100=0

=>x=-100

ai trả lời giúp mik đi mà

\(189:\left[628-\left(2x-1\right)^2\right]=3^2\cdot7\)

=>\(628-\left(2x-1\right)^2=\dfrac{189}{63}=3\)

=>\(\left(2x-1\right)^2=628-3=625\)

=>\(\left[{}\begin{matrix}2x-1=25\\2x-1=-25\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}2x=26\\2x=-24\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=13\\x=-12\end{matrix}\right.\)

\(189:\left[628-\left(2x-1\right)^2\right]=3^2.7\)
\(\Rightarrow628-\left(2x-1\right)^2=\dfrac{189}{63}\)
\(\Rightarrow628-\left(2x-1\right)^2=3\)
\(\Rightarrow\left(2x-1\right)^2=625\)
\(\Rightarrow\left[{}\begin{matrix}2x-1=25\\2x-1=-25\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=13\\x=-12\end{matrix}\right.\)

luoi lam

\(C=\dfrac{4}{3.5}+\dfrac{4}{5.7}+\dfrac{4}{7.9}+...+\dfrac{4}{97.99}\)
\(=2\left(\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{97.99}\right)\)
\(=2\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{97}-\dfrac{1}{99}\right)\)
\(=2\left(\dfrac{1}{3}-\dfrac{1}{99}\right)\)
\(=2\cdot\dfrac{32}{99}=\dfrac{64}{99}\)
\(D=\dfrac{18}{2.5}+\dfrac{18}{5.8}+...+\dfrac{18}{203.206}\)
\(=6\left(\dfrac{3}{2.5}+\dfrac{3}{5.8}+...+\dfrac{3}{203.206}\right)\)
\(=6\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+...+\dfrac{1}{203}-\dfrac{1}{206}\right)\)
\(=6\left(\dfrac{1}{2}-\dfrac{1}{206}\right)\)
\(=6\cdot\dfrac{51}{103}=\dfrac{306}{103}\)
\(\Rightarrow\dfrac{C}{D}=\dfrac{\dfrac{64}{99}}{\dfrac{306}{103}}=\dfrac{3296}{15147}\)

ai trả lời giúp mik với

a: Hai tia trùng nhau là OA,OB

Hai tia đối nhau là Bx,BO; Ax;AO

b: Trên tia Ox, ta có: OA<OB

nên A nằm giữa O và B

c: Ta có: A nằm giữa O và B

=>OA+AB=OB

=>AB+2=4

=>AB=2(cm)

ta có: A nằm giữa O và B

mà AO=AB(=2cm)

nên A là trung điểm của OB

a: Hai tia trùng nhau là OA,OB

Hai tia đối nhau là Bx,BO; Ax;AO

b: Trên tia Ox, ta có: OA<OB

nên A nằm giữa O và B

c: Ta có: A nằm giữa O và B

=>OA+AB=OB

=>AB+2=4

=>AB=2(cm)

ta có: A nằm giữa O và B

mà AO=AB(=2cm)

nên A là trung điểm của OB

1.yes, I do

2.I often watch horror film.

3.I like to watch animated movies. Because it is very funny and the characters are cute.

4.yes, I did. it was very scary