a, y \(\times\) \(\dfrac{4}{3}\) = \(\dfrac{16}{9}\)

    y         =    \(\dfrac{16}{9}\) : \(\dfrac{4}{3}\)

    y         = \(\dfrac{4}{3}\)

b, ( y - \(\dfrac{1}{2}\)) + 0,5 = \(\dfrac{3}{4}\)

    y - 0,5 + 0,5 = \(\dfrac{3}{4}\)

   y                   = \(\dfrac{3}{4}\)

c, \(\dfrac{4}{5}-\dfrac{2}{5}y\) = 0,2

   0,8 - 0,4y = 0,2

           0,4y = 0,8 - 0,2

           0,4y  = 0,6

               y = 1,5

d, (y + \(\dfrac{3}{4}\)) \(\times\) \(\dfrac{5}{7}\) = \(\dfrac{10}{9}\)

    y + \(\dfrac{3}{4}\)           = \(\dfrac{10}{9}\) : \(\dfrac{5}{7}\)

   y + \(\dfrac{3}{4}\)            = \(\dfrac{14}{9}\)

y                    = \(\dfrac{14}{9}\) - \(\dfrac{3}{4}\)

 y                   =   \(\dfrac{29}{36}\)

e, y : \(\dfrac{5}{4}\)         = \(\dfrac{9}{5}\)  + \(\dfrac{1}{2}\)

   y : \(\dfrac{5}{4}\)         =   \(\dfrac{23}{10}\)

  y                =      \(\dfrac{23}{10}\)

  y               =   \(\dfrac{23}{8}\)

f, y \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{3}{2}\) \(\times\) y   = \(\dfrac{4}{5}\)

   y \(\times\) ( \(\dfrac{1}{2}+\dfrac{3}{2}\))      =  \(\dfrac{4}{5}\)

   2y                       = \(\dfrac{4}{5}\)

    y                        = \(\dfrac{2}{5}\)

a/b nhân 4 cộng 1/6 = 17/6 số phải tìm là bao nhiêu

Cậu cho nhiều quá

Mỗi bài mình làm một dạng thôi nhé!

1) \(\left(\frac{3}{2}-\frac{x}{y}\right)+\frac{5}{7}=\frac{11}{14}\)

\(\Rightarrow\frac{x}{y}=\frac{3}{2}-\left(\frac{11}{14}-\frac{5}{7}\right)=\frac{10}{7}\)

2) a) 

\(\frac{17}{9}+\frac{19}{13}+\frac{14}{6}+\frac{7}{13}+\frac{10}{6}+\frac{1}{9}\)

\(=\left(\frac{17}{9}+\frac{1}{9}\right)+\left(\frac{19}{13}+\frac{7}{13}\right)+\left(\frac{14}{6}+\frac{10}{6}\right)\)

\(=2+2+4\)

\(=8\)

3) a) 

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{42}\)

\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{6.7}\)

\(A=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{6}-\frac{1}{7}\)

\(A=\frac{1}{1}-\frac{1}{7}=\frac{6}{7}\)

4) a)

\(y.\frac{5}{6}=1+\frac{1}{2}\)

\(\Rightarrow y.\frac{5}{6}=\frac{3}{2}\)

\(\Rightarrow y=\frac{3}{2}.\frac{6}{5}=\frac{9}{5}\)

a) y = 5/14 : 6/7

y = 5/12 

vậy y = 5/12

b) y = 4/9 x 2/3 

y = 8/27 

vậy t = 8/27

c) y = 1/2 - 3/10 

y = 1/5

vậy y = 1/5

d) y = 5/6 - 1/3

y = 1/2

vậy y = 1/2

Bài 2:

\(\dfrac{a+b}{a-b}=\dfrac{c+a}{c-a}\)

\(\Rightarrow\dfrac{a+b}{c+a}=\dfrac{a-b}{c-a}=\dfrac{a+b+a-b}{c+a+c-a}=\dfrac{a}{c}\) (T/c dãy tỷ số = nhau)

\(\Rightarrow\dfrac{a+b}{c+a}=\dfrac{a}{c}\Rightarrow c\left(a+b\right)=a\left(c+a\right)\)

\(\Rightarrow ac+bc=ac+a^2\Rightarrow a^2=bc\)

( 2 x y + 2/15 ) x 3 = 4/5

( 2 x y + 2/15 )      = 4/5 : 3 

( 2 x y + 2/15 )      =   4/15

 2 x y                    = 4/15 - 2/15 

2 x y                     =     2/15

     y                      =     2/15 :2 

   y                          =    1/15

(2 x y + 2/15) x 3 = 4/5 

2 x y + 2/15) = 4/5 : 3 

2 x y + 2/15 = 4/15 

2 x y = 4/15 - 2/15 

2 x y = 2/15 

y = 2/15 : 2 

y = 1/15 

7/9 x (2 - 1/3 x y) = 14/15 

(2 - 1/3 x y) = 14/15 : 7/9 

(2 - 1/3 x y) = 6/5 

2 - y = 6/5 x 1/3 

2 - y = 2/5 

y = 2/5 + 2 

y = 12/5 

4/21 + 5 x y - 8/7 = 1/3 

4/21 + 5 x y = 1/3 + 8/7 

4/21 + 5 x y = 31/21 

5 x y = 31/21 - 4/21 

5 x y = 9/7 

y = 9/7 : 5 

y = 9/35 

7/12 x y - 3/12 x y = 5 

y x (7/12 - 3/12) = 5 

y x 1/3 = 5 

y = 5 : 1/3 

y = 15 

Bài 3 :

Cách 1 :

( \(\frac{7}{9}\)+\(\frac{5}{6}\)) x \(\frac{3}{5}\)

= \(\frac{29}{18}\)x\(\frac{3}{5}\)

= \(\frac{29}{30}\)

Cách 2 : 

( \(\frac{7}{9}\)+\(\frac{5}{6}\)) x \(\frac{3}{5}\)

= \(\frac{7}{9}\)x \(\frac{3}{5}\)+\(\frac{5}{6}\)x\(\frac{3}{5}\)

= \(\frac{7}{15}\)+\(\frac{1}{2}\)

= \(\frac{29}{30}\)

Bài 1 :

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

X = \(\frac{9}{14}\):\(\frac{3}{7}\)

X = \(\frac{3}{14}\)

Vậy X = \(\frac{3}{14}\)

X : \(\frac{5}{9}\)=\(\frac{3}{10}\)

X = \(\frac{3}{10}\)x\(\frac{5}{9}\)

X = \(\frac{1}{6}\)

Vậy X = \(\frac{1}{6}\)

ミ★ɦàղ ζɦ¡êղ ʑ¡ղ★彡 bạn làm thêm cả bài 2,3,4,5 nữa nha.