= 3/4 + 1/3 = 13/12

5/4 x X = 5/8

X = 5/8 : 5/4

X = 1/2

vậy X = ...

\(\dfrac{3}{5}:\dfrac{4}{5}+\dfrac{1}{2}\times\dfrac{2}{3}=\dfrac{3}{4}+\dfrac{1}{3}+\dfrac{9}{12}+\dfrac{4}{12}=\dfrac{11}{12}\)

\(\dfrac{5}{4}\times x=\dfrac{5}{8}\)

\(x=\dfrac{5}{8}:\dfrac{5}{4}\)

\(x=\dfrac{1}{2}\)

Tính giá trị biểu thức
   \(\dfrac{3}{5}:\dfrac{4}{5}+\dfrac{1}{2}x\dfrac{2}{3}=\dfrac{3}{5}x\dfrac{5}{4}+\dfrac{1}{3}=\dfrac{3}{4}+\dfrac{1}{3}=\dfrac{9+4}{12}=\dfrac{13}{12}\)  

Tìm x
    \(\dfrac{5}{4}\)xX=\(\dfrac{3}{8}+\dfrac{1}{4}\)
    \(\dfrac{5}{4}\)xX=\(\dfrac{5}{8}\)
    x=\(\dfrac{5}{8}\) :\(\dfrac{5}{4}\)
    x=\(\dfrac{1}{2}\)

\(\Leftrightarrow2.5:x=2+\dfrac{2}{3}-2-\dfrac{1}{5}=\dfrac{7}{15}\)

hay \(x=\dfrac{5}{2}:\dfrac{7}{15}=\dfrac{5}{2}\cdot\dfrac{15}{7}=\dfrac{75}{14}\)

=>x=7/3:2/3=7/2

X là : 21/6

\(x\times\dfrac{2}{3}=\dfrac{7}{3}\)

\(x=\dfrac{7}{3}:\dfrac{2}{3}\)

\(x=\dfrac{7}{2}\)

lớp 7 có bài đó lun hẻ 

có j đó sai sai :>

\(3x^2y-7yx+5x^5-6yx^2-3x^3+8xy-5x^5-x^3\)

bậc là năm :v

a)\(f\left(1\right)=2.1^2+5.1-3=2+5-3=4\)

\(f\left(0\right)=0+0-3=-3\)

\(f\left(1,5\right)=2.\left(1,5\right)^2-5.1,5-3=4,5-7,5-3=-6\)

b)\(f\left(3\right)=3a-3=9=>>3a=12=>a=4\)

\(f\left(5\right)=5a-3=11=>5a=14=>a=\dfrac{14}{5}\)

\(f\left(-1\right)=-a-3=6=>-a=9=>a=-9\)

     30% . x - x - \(\dfrac{5}{6}\) = \(\dfrac{1}{3}\)

\(\Rightarrow\) (\(\dfrac{3}{10}\) - 1) . x = \(\dfrac{1}{3}+\dfrac{5}{6}\)

\(\Rightarrow\) \(-\dfrac{7}{10}\) . x = \(\dfrac{7}{6}\)

\(\Rightarrow\) x = \(-\dfrac{3}{5}\)

KO ghi đề nhé

\(\dfrac{3}{10}.x-x=\dfrac{1}{3}+\dfrac{5}{6}\)

\(x\left(\dfrac{3}{10}-1\right)=\dfrac{2}{6}+\dfrac{5}{6}\)

\(x.\dfrac{-7}{10}=\dfrac{7}{6}\)

\(x=\dfrac{7}{10}:\dfrac{-7}{6}\)

\(x=\dfrac{7}{10}.\dfrac{6}{-7}\)

\(x=\dfrac{42}{-70}\)

\(x=\dfrac{6}{-10}\)

\(x=\dfrac{3}{-5}\)

Vậy \(x=\dfrac{3}{-5}\)

\(30\%.x-x-\dfrac{5}{6}=\dfrac{1}{3}\) 

     \(x.\left(30\%-1\right)=\dfrac{1}{3}+\dfrac{5}{6}\) 

               \(x.\dfrac{-7}{10}=\dfrac{7}{6}\)  

                       \(x=\dfrac{7}{6}:\dfrac{-7}{10}\) 

                       \(x=\dfrac{-5}{3}\)

\(\dfrac{9}{7}x+\dfrac{5}{7}x=\dfrac{2}{3}\)

\(\Leftrightarrow x\left(\dfrac{9}{7}+\dfrac{5}{7}\right)=\dfrac{2}{3}\)

\(\Leftrightarrow\dfrac{14}{7}x=\dfrac{2}{3}\)

\(\Leftrightarrow2x=\dfrac{2}{3}\)

\(\Leftrightarrow x=\dfrac{2}{3}:2\)

\(\Leftrightarrow x=\dfrac{2}{3}\times\dfrac{1}{2}\)

\(\Leftrightarrow x=\dfrac{2}{6}\)

\(\Leftrightarrow x=\dfrac{1}{3}\)

`a)`

`@f(1)=2.1^2+5.1-3=2.1+5-3=2+5-3=4`

`@f(0)=2.0^2+5.0-3=-3`

`@f(1,5)=2.(1,5)^2+5.1,5-3=4,5+7,5-3=9`

_____________________________________________________

`b)`

`***f(3)=9`

`=>3a-3=9`

`=>3a=12=>a=4`

`***f(5)=11`

`=>5a-3=11`

`=>5a=14=>a=14/5`

`***f(-1)=6`

`=>-a-3=6`

`=>-a=9=>a=-9`

a: f(1)=2+5-3=4

f(0)=-3

f(1,5)=4,5+7,5-3=9

b: f(3)=9 nên 3a-3=9

hay a=4

f(5)=11 nên 5a-3=11

hay a=14/5

f(-1)=6 nên -a-3=6

=>-a=9

hay a=-9

Không có dấu "=" nên đây không được gọi là phương trình bạn nhé. Bạn cần xem lại đề.