\(a.\dfrac{3}{4}:x=-\dfrac{1}{2}\\ x=\dfrac{3}{4}:\left(-\dfrac{1}{2}\right)\\ x=-\dfrac{3}{2}\\ b.x:\left(-\dfrac{2}{3}\right)=-\dfrac{5}{6}\\ x=\left(-\dfrac{5}{6}\right)\cdot\left(-\dfrac{2}{3}\right)\\ x=\dfrac{5}{9}\\ c.\dfrac{1}{2}:x-\dfrac{1}{2}=-\dfrac{3}{4}\\ \dfrac{1}{2}:x=-\dfrac{1}{4}\\ x=\dfrac{1}{2}:\left(-\dfrac{1}{4}\right)\\ x=-2\\ d.\dfrac{1}{2}\cdot x+\dfrac{3}{4}=-\dfrac{5}{6}\\ \dfrac{1}{2}\cdot x=-\dfrac{19}{12}\\ x=\dfrac{-19}{12}:\dfrac{1}{2}=-\dfrac{19}{12}\cdot2\\ x=-\dfrac{19}{6}\)

\(e.x:\dfrac{1}{2}+\dfrac{1}{2}=-\dfrac{5}{6}\\ x:\dfrac{1}{2}=-\dfrac{4}{3}\\ x=-\dfrac{4}{3}\cdot\dfrac{1}{2}\\ x=-\dfrac{2}{3}\\ g.\dfrac{4}{3}-\dfrac{1}{2}\cdot x=\dfrac{1}{2}\\ \dfrac{1}{2}\cdot x=\dfrac{5}{6}\\ x=\dfrac{5}{6}:\dfrac{1}{2}=\dfrac{5}{6}\cdot2\\ x=\dfrac{5}{3}\\ h.\dfrac{3}{8}\cdot x-\dfrac{1}{2}=\dfrac{3}{4}\\ \dfrac{3}{8}\cdot x=\dfrac{1}{4}\\ x=\dfrac{1}{4}:\dfrac{3}{8}=\dfrac{1}{4}\cdot\dfrac{8}{3}\\ x=\dfrac{2}{3}\)

mình làm lại câu h xíu

\(\dfrac{3}{8}\cdot x-\dfrac{1}{2}=\dfrac{3}{4}\\ \dfrac{3}{8}\cdot x=\dfrac{5}{4}\\ x=\dfrac{5}{4}:\dfrac{3}{8}=\dfrac{5}{4}\cdot\dfrac{8}{3}\\ x=\dfrac{10}{3}\)

\(a.\dfrac{3}{2}-4\cdot\left(\dfrac{1}{2}+\dfrac{3}{4}\right)\\ =\dfrac{3}{2}-4\cdot\dfrac{5}{4}\\ =\dfrac{3}{2}-5=-\dfrac{7}{2}\\ b.\left(-\dfrac{1}{3}+\dfrac{5}{6}\right)\cdot11-7\\ =\dfrac{1}{2}\cdot11-7\\ =\dfrac{11}{2}-7=-\dfrac{3}{2}\\ c.\left(\dfrac{5}{8}+\dfrac{-2}{7}\right):\dfrac{3}{4}+\left(\dfrac{3}{8}-\dfrac{5}{7}\right):\dfrac{3}{4}\\ =\left(\dfrac{5}{8}+\dfrac{-2}{7}\right)\cdot\dfrac{4}{3}+\left(\dfrac{3}{8}-\dfrac{5}{7}\right)\cdot\dfrac{4}{3}\\ =\dfrac{4}{3}\cdot\left(\dfrac{5}{8}-\dfrac{2}{7}+\dfrac{3}{8}-\dfrac{5}{7}\right)\)

\(\dfrac{4}{3}\cdot\left[\left(\dfrac{5}{8}+\dfrac{3}{8}\right)-\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\right]\\ =\dfrac{4}{3}\cdot\left(1-1\right)=\dfrac{4}{3}\cdot0=0\)

\(d.\dfrac{\dfrac{3}{4}-\dfrac{3}{5}+\dfrac{3}{7}+\dfrac{3}{11}}{\dfrac{13}{4}-\dfrac{13}{5}+\dfrac{13}{7}+\dfrac{13}{11}}\\ =\dfrac{3\cdot\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{11}\right)}{13\cdot\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{11}\right)}=\dfrac{3}{13}\)

a) 

\(\dfrac{3}{2}-4\left(\dfrac{1}{2}+\dfrac{3}{4}\right)\\ =\dfrac{3}{4}-4\left(\dfrac{2}{4}+\dfrac{3}{4}\right)\\ =\dfrac{3}{4}-4\cdot\dfrac{5}{4}\\ =\dfrac{3}{4}-5\\ =-\dfrac{17}{4}\) 

b) 

\(\left(-\dfrac{1}{3}+\dfrac{5}{6}\right)\times11-7\\ =\left(-\dfrac{2}{6}+\dfrac{5}{6}\right)\times11-7\\ =\dfrac{1}{2}\times11-7\\ =\dfrac{11}{2}-7\\ =-\dfrac{3}{2}\)

c) 

\(\left(\dfrac{5}{8}+\dfrac{-2}{7}\right):\dfrac{3}{4}+\left(\dfrac{3}{8}-\dfrac{5}{7}\right):\dfrac{3}{4}\\ =\left(\dfrac{5}{8}+\dfrac{-2}{7}\right)\times\dfrac{4}{3}+\left(\dfrac{3}{8}-\dfrac{5}{7}\right)\times\dfrac{4}{3}\\ =\dfrac{4}{3}\times\left(\dfrac{5}{8}+\dfrac{-2}{7}+\dfrac{3}{8}-\dfrac{5}{7}\right)\times\dfrac{4}{3}\\ =\left(1-1\right)\times\dfrac{4}{3}\\ =0\times\dfrac{4}{3}\\ =0\)

d) 

\(M=\dfrac{\dfrac{3}{4}-\dfrac{3}{5}+\dfrac{3}{7}+\dfrac{3}{11}}{\dfrac{13}{4}-\dfrac{13}{5}+\dfrac{13}{7}+\dfrac{13}{11}}\\ =\dfrac{3\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{11}\right)}{13\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{11}\right)}\\ =\dfrac{3}{13}\)

\(a.\left(-\dfrac{9}{34}\right)\cdot\dfrac{17}{4}=-\dfrac{9}{8}\\ b.\left(-\dfrac{20}{41}\right)\cdot\left(-\dfrac{4}{5}\right)=\dfrac{16}{41}\\ c.1\dfrac{1}{7}\cdot\left(-3\dfrac{1}{2}\right)=\dfrac{8}{7}\cdot\left(-\dfrac{7}{2}\right)=-4\\ d.\left(-\dfrac{5}{2}\right):\dfrac{3}{4}=\left(-\dfrac{5}{2}\right)\cdot\dfrac{4}{3}=-\dfrac{10}{3}\\ e.\left(-\dfrac{3}{4}\right):\left(-1\dfrac{1}{3}\right)=\left(-\dfrac{3}{4}\right)\cdot\left(-\dfrac{3}{4}\right)=\dfrac{9}{16}\\ g.\left(-5\right):\left(-2\dfrac{1}{2}\right)=\left(-5\right)\cdot\left(-\dfrac{2}{5}\right)=2\)

\(a)-\dfrac{9}{34}\times\dfrac{17}{4}\\ =\dfrac{-9}{17\times2}\times\dfrac{17}{4}\\ =\dfrac{-9}{8}\\ b)-\dfrac{20}{41}\times-\dfrac{4}{5}\\ =\dfrac{4\times5}{41}\times\dfrac{-4}{5}\\ =-\dfrac{16}{41}\\ c)1\dfrac{1}{7}\times\left(-3\dfrac{1}{2}\right)\\ =\dfrac{8}{7}\times\dfrac{-7}{2}\\ =-4\\ d)-\dfrac{5}{2}:\dfrac{3}{4}\\ =-\dfrac{5}{2}\times\dfrac{4}{3}\\ =\dfrac{-10}{3}\\ e)-\dfrac{3}{4}:\left(-1\dfrac{1}{3}\right)\\ =-\dfrac{3}{4}:-\dfrac{4}{3}\\ =-\dfrac{3}{4}\times-\dfrac{3}{4}\\ =\dfrac{9}{16}\\ g)-5:\left(-2\dfrac{1}{2}\right)\\ =-5:-\dfrac{5}{2}\\ =-5\times-\dfrac{2}{5}\\ =2\)

\(9x-3=14\)
\(9x=14+3=17\)
\(9x=17\)
\(x=17\div9=\dfrac{17}{9}\)
\(x=\dfrac{17}{9}\)
~nhớ tk và hok tốt~
@Đinh Sơn Tùng

-120

-279

-111

tick mình nhé

Mình cần gấp ạ

Bạn giúp mình với

a) \(A=\dfrac{2x-1}{x+2}=\dfrac{2x+4-5}{x+2}=2-\dfrac{5}{x+2}\)

Để A là số nguyên thì \(\dfrac{5}{x+2}\) phải nguyên

\(\Rightarrow x+2\) ∈ Ư(5) = {1; -1; 5; -5} 

\(\Rightarrow x\in\left\{-1;-3;3;-7\right\}\)

b) Để A là số tự nhiên thì: \(x\in\left\{-3;3;-7\right\}\)

c) x là số tự nhiên để A là số nguyên => \(x=3\) 

d) x nguyên lớn nhất để A nhận giá trị nguyên => \(x=3\)

e) x nguyên nhỏ nhất để A nhận giá trị nguyên => `x=-7` 

25.[(100+200) - (321 - 121)]

= 25.(300 - 200)

= 25.100

= 2500 

2500

Chiều dài hình chữ nhật đó sau khi tăng thêm 20% bằng:

\(100\%+20\%=1,2\) (chiều dài ban đầu)

Chiều rộng hình chữ nhật đó sau khi giảm đi 20% bằng:

\(100\%-20\%=0,8\) (chiều rộng ban đầu)

Sau khi thay đổi kích thước, diện tích hình chữ nhật đã giảm đi:

\(100\%-\left(1,2.0,8\right)=4\%\) (diện tích ban đầu)

Diện tích hình chữ nhật ban đầu là:

\(30:4\%=750\left(m^2\right)\)

\(a)2x-4=0\\ 2x=4\\ x=\dfrac{4}{2}\\ x=2\\ b)2x-7=1\\ 2x=7+1\\ 2x=8\\ x=\dfrac{8}{2}\\ x=4\\ c)3x-9=6\\ 3x=9+6\\ 3x=15\\ x=\dfrac{15}{3}\\ x=5\\ d)5-2x=3\\ -2x=3-5\\ -2x=-2\\ x=\dfrac{-2}{-2}\\ x=1\\ e)8-2x=6\\ -2x=6-8\\ -2x=-2\\ x=\dfrac{-2}{-2}\\ x=1\\ f)3x+5=11\\ 3x=11-5\\ 3x=6\\ x=\dfrac{6}{3}\\ x=2\\ g)4x+4=16\\ 4x=16-4\\ 4x=12\\ x=\dfrac{12}{4}\\ x=3\\ h)7+5x=12\\ 5x=12-7\\ 5x=5\\ x=\dfrac{5}{5}\\ x=1\\ i)10+3x=34\\ 3x=34-10\\ 3x=24\\ x=\dfrac{24}{3}\\ x=8\)