\(2\frac{3}{4}x=3\frac{1}{7}:0,01\)

=> \(\frac{11}{4}x=\frac{22}{7}:\frac{1}{100}\)

=> \(x=\frac{\frac{22}{7}\cdot100}{\frac{11}{4}}=\frac{\frac{2200}{7}}{\frac{11}{4}}=\frac{2200}{7}\cdot\frac{4}{11}=\frac{800}{7}\)

\(2\frac{1}{3}:\frac{1}{3}=\frac{7}{9}:x\)

=> \(\frac{7}{3}:\frac{1}{3}=\frac{7}{9}:x\)

=> \(\frac{7}{3}\cdot\frac{3}{1}=\frac{7}{9}:x\)

=> \(\frac{7}{9}:x=7\)

=> \(x=\frac{7}{9}:7=\frac{7}{9}\cdot\frac{1}{7}=\frac{1}{9}\)

\(3,2x+\left(-1,2\right)x+2,7=-4,9\)

=> \(\left[3,2+\left(-1,2\right)\right]x=-7,6\)

=> 2.x = -7,6

=> x = -3,8

\(x:\frac{9}{14}=\frac{7}{3}:x\)

=> \(x\cdot\frac{14}{9}=\frac{7}{3}\cdot\frac{1}{x}\)

=> \(\frac{14x}{9}=\frac{7}{3x}\)

nên sửa lại đề này

\(\frac{37-x}{x+13}=\frac{3}{7}\)

=> 7(37 - x) = 3(x + 13)

=> 259 - 7x = 3x + 39

=> 259 - 7x - 3x - 39 = 0

=> 220 - 10x = 0

=> 220  = 10x

=> x = 22

\(\frac{x}{15}=\frac{-60}{x}\)=> x² = -900 => x không thỏa mãn

a) \(2\frac{3}{4}.x=3\frac{1}{7}:0,01\)

\(=>2\frac{3}{4}.x=2200=>\frac{11}{4}x=2200=>x=800\)

b) \(2\frac{1}{3}:\frac{1}{3}=\frac{7}{9}:x\)

\(=>7=\frac{7}{9}:x\)

hay \(\frac{7}{9}:x=7=>x=\frac{1}{9}\)

c) \(3,2x+\left(-1,2\right)x+2,7=-4,9\)

\(=>2x+2,7=-4,9\)

\(=>2x=-7,6=>x=-3,8\)

d) \(x:\frac{9}{14}=\frac{7}{3}:x\)

\(=>x.x=\frac{7}{3}.\frac{9}{14}\)

\(=>x^2=\frac{3}{2}\)

....................( ko hiểu)

e) \(\frac{37-x}{x+13}=\frac{3}{7}\)

\(=>7.\left(37-x\right)=3.\left(x+13\right)\)

\(=>259-7x=3x+39\)

\(-7x-3x=39-269\)

\(=>-10x=-220=>x=22\)

f) \(\frac{x}{15}=\frac{-60}{x}\)

\(=>x.x=-60.15=>x^2=-900=>x=-30\)

cậu có thể tham khảo bài alfm trên đây ạ, chúc học tốt:>

\(\frac{6}{11}x=\frac{9}{2}y=\frac{18}{5}z\Rightarrow\frac{6x}{11.18}=\frac{9y}{2.18}=\frac{18z}{5.18}\)

\(\Rightarrow\frac{-x}{-33}=\frac{y}{4}=\frac{z}{5}=\frac{-x+y+z}{-33+4+5}=\frac{-120}{-24}=5\)

\(\Rightarrow x=165;y=20;z=25\)

1/ ĐÁP ÁN:

\(\frac{-9}{33}=\frac{3}{-11}\); \(\frac{15}{9}=\frac{5}{3}\); \(\frac{-12}{19}=\frac{60}{-95}\)

2/ ĐÁP ÁN:

\(\frac{-7}{20}=\frac{3}{-18}=\frac{-9}{54}\ne\frac{12}{18}=\frac{-10}{-15}\ne\frac{14}{20}\)

3/ ĐÁP ÁN:

\(\frac{2}{3}=\frac{40}{60}\); \(\frac{3}{4}=\frac{45}{60}\); \(\frac{4}{5}=\frac{48}{60}\); \(\frac{5}{6}=\frac{50}{60}\)

a) \(\frac{-8}{3}+\frac{7}{5}+\frac{-71}{15}\)< \(x\) < \(\frac{-13}{7}+\frac{19}{14}+\frac{-7}{2}\)

Ta có: \(\frac{-8}{3}+\frac{7}{5}+\frac{-71}{15}\)

=\(\frac{-40}{15}+\frac{21}{15}+\frac{-71}{15}\)

=\(\frac{-90}{15}\)

=\(-6\)

Ta có: \(\frac{-13}{7}+\frac{19}{14}+\frac{-7}{2}\)

=\(\frac{-26}{14}+\frac{19}{14}+\frac{-49}{14}\)

=\(\frac{-56}{14}\)

=\(-4\)

=> \(-6\)< \(x\)<\(-4\)

=> \(x=-5\)

b)\(\frac{5}{17}+\frac{-4}{9}+\frac{-20}{31}+\frac{12}{17}+\frac{-11}{31}\)< \(\frac{x}{9}\)<\(\frac{-3}{7}+\frac{7}{15}+\frac{4}{-7}+\frac{8}{15}+\frac{2}{3}\)

Ta có: \(\frac{5}{17}+\frac{-4}{9}+\frac{-20}{31}+\frac{12}{17}+\frac{-11}{31}\)

=\(\left(\frac{5}{17}+\frac{12}{17}\right)+\left(\frac{-20}{31}+\frac{-11}{31}\right)+\frac{-4}{9}\)

=\(1+\left(-1\right)+\frac{-4}{9}\)

=\(0+\frac{-4}{9}\)

=\(\frac{-4}{9}\)

Ta có: \(\frac{-3}{7}+\frac{7}{15}+\frac{4}{-7}+\frac{8}{15}+\frac{2}{3}\)

=\(\frac{-3}{7}+\frac{7}{15}+\frac{-4}{7}+\frac{8}{15}+\frac{2}{3}\)

=\(\left(\frac{-3}{7}+\frac{-4}{7}\right)+\left(\frac{7}{15}+\frac{8}{15}\right)+\frac{2}{3}\)

=\(\left(-1\right)+1+\frac{2}{3}\)

=\(0+\frac{2}{3}\)

=\(\frac{2}{3}\)

=> \(\frac{-4}{9}\)< \(\frac{x}{9}\)<\(\frac{2}{3}\)

=

=> \(\frac{-4}{9}\)<\(\frac{x}{9}\)<\(\frac{6}{9}\)

=> \(-4\)< \(x\)<\(6\)

=>\(x\in\left\{-3;-2;-1;0;1;2;3;4;5\right\}\)

Biết rồi mà đi đố người khác . Chịu chị luôn em lạy 2 tay

tìm n   N để \(\frac{n}{n+1}\) + \(\frac{n}{n+2}\) là số tự nhiên

giúp mik với sắp thi r

1. 15/60 = 1/4

-7/5 = -7/5

6/15 = 2/5

28/-20 = -7/5

3/12 = 1/4

Vậy 15/60 = 3/12; -7/5 = 28/-20.

2. a. => 8.9 = 3.(x - 1) 

=> 72 : 3 = x - 1

=> 24 = x - 1

=> x = 25

b. => -x.x = -9.4

=> -x.x = -36

=> -x.x = -6.6

=> x = 6

c. => x.(x + 1) = 4.18

=> x.(x + 1) = 72

=> x.(x + 1) = 8.9 hoặc x.(x + 1) = (-9).(-8)

=> x.(x + 1) = 8.(8 + 1) hoặc x.(x + 1) = (-9).(-9 + 1)

Vậy x thuộc {-9; 8}.

=>(5/17+12/17)+(-20/31-11/31)-4/9<=x/9<=(-3/7-4/7)+(7/15+8/15)+2/3

=>-4/9<=x/9<=6/9

=>-4<=x<=6

hay \(x\in\left\{-4;-3;-2;-1;0;...;6\right\}\)

a) \(\frac{x}{3}=\frac{10}{15}\Leftrightarrow15x=30\Leftrightarrow x=2\)

b, \(\frac{x}{4}=\frac{9}{x}\Leftrightarrow x^2=36\Leftrightarrow\orbr{\begin{cases}x=6\\x=-6\end{cases}}\)

c, \(\frac{5+x}{3+x}=\frac{9}{7}\left(x\ne-3\right)\Leftrightarrow35+7x=27+9x\Leftrightarrow-2x=-8\Leftrightarrow x=4\left(tmđk\right)\)

a) \(\left(3\frac{1}{2}-2x\right).3\frac{1}{3}=7\frac{1}{3}\)

 \(\left(\frac{7}{2}-2x\right).\frac{10}{3}=\frac{22}{3}\)

  \(\frac{7}{2}-2x=\frac{11}{5}\)

              \(2x=\frac{13}{10}\)

                \(x=\frac{13}{20}\)

Vậy ...

b) \(\frac{4}{9}x=\frac{9}{8}-0,125\)

   \(\frac{4}{9}x=1\)

         \(x=\frac{9}{4}\)

Vậy...

a) \(x+\frac{-7}{15}=-1\frac{1}{20}\)

                    \(x=\frac{-21}{20}\)\(+\frac{7}{15}\)

                    \(x=\frac{-7}{12}\)

b) \(\left(3\frac{1}{2}-x\right)\cdot1\frac{1}{4}=-1\frac{1}{20}\)

         \(\left(\frac{7}{2}-x\right)\cdot\frac{5}{4}=-\frac{21}{20}\)

                        \(\frac{7}{2}-x=\frac{-21}{20}\cdot\frac{4}{5}\)

                         \(\frac{7}{2}-x=\frac{-21}{25}\)

                                    \(x=\frac{7}{2}+\frac{21}{25}\)     

                                   \(x=\frac{217}{50}\)

Hc tốt #