a) 

( 4x - 9 ) ( 2,5 + (-7/3) . x ) = 0

\(\Rightarrow\orbr{\begin{cases}4x-9=0\\2,5+\frac{-7}{3}x=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{9}{4}\\x=\frac{15}{14}\end{cases}}\)

P/s: đợi xíu làm câu b

b) \(\frac{1}{x\left(x+1\right)}\cdot\frac{1}{\left(x+1\right)\left(x+2\right)}\cdot\frac{1}{\left(x+2\right)\left(x+3\right)}-\frac{1}{x}=\frac{1}{2015}\)

\(\frac{1}{x}-\frac{1}{x+1}+\frac{1}{x+1}-\frac{1}{x+2}+\frac{1}{x+2}-\frac{1}{x+3}-\frac{1}{x}=\frac{1}{2015}\)

\(\frac{-1}{x+3}=\frac{1}{2015}\)

\(\Leftrightarrow x+3=-2015\)

\(\Leftrightarrow x=-2018\)

Vậy,.........

A/ Ta có số nào nhân với 0 cx = 0 

Vậy từ đó suy ra 2 trường hợp 

TH1\(4x-9=0\)

\(=>x=\frac{9}{4}\)

TH2 \(2,5+-\frac{7}{3}x=0\)

 \(=>x=\frac{15}{14}\)

\(7.\frac{-1}{10}-\frac{2}{3}.4,8-2.\frac{-1}{10}+\frac{7}{9}.4,8\)8

\(\frac{-7}{10}-\frac{16}{5}-\frac{1}{5}+\frac{56}{15}\)

  \(=\frac{-11}{30}\)

a) \(\left(x-\frac{1}{2}\right).\frac{1}{3}+\frac{5}{7}=9\frac{5}{7}\)

\(\left(x-\frac{1}{2}\right).\frac{1}{3}=9\frac{5}{7}-\frac{5}{7}\)

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

\(x=27+\frac{1}{2}\)

\(x=\frac{55}{2}\)

b)\(\frac{1}{2}.x+150\%.x=2014\)

\(\left(\frac{1}{2}+150\%\right)x=2014\)

\(2x=2014\)

\(x=2014:2\)

\(x=1007\)

c) \(2-\left|\frac{3}{4}\right|=\frac{7}{2}\)???????

và bài này nữa

tính nhanh

a, \(5\frac{7}{5}\cdot4\frac{2}{7}+5\frac{5}{7}\cdot4\frac{2}{7}\)

b, \(b,\frac{-7}{11}\cdot\frac{4}{19}+\frac{-7}{19}\cdot\frac{7}{11}+2\frac{7}{19}\)

cảm ơn giúp nhiều

\(a,\left(x-\frac{1}{2}\right)\frac{1}{3}+\frac{5}{7}=9\frac{5}{7}\)

\(\Rightarrow\frac{x}{3}-\frac{1}{6}+\frac{5}{7}=\frac{68}{7}\)

\(\Rightarrow\frac{x}{3}-\frac{1}{6}=\frac{63}{7}=9\)

\(\Rightarrow\frac{x}{3}=9+\frac{1}{6}=\frac{55}{6}\)

\(\Rightarrow x=55:2=27,5\)

\(b,\frac{1}{2}.x+150\%.x=2014\)

\(\Rightarrow\frac{x}{2}+\frac{3}{2}.x=2014\)

\(\Rightarrow2x=2014\)

\(\Rightarrow x=2014:2=1007\)

\(c,2-\left|\frac{3}{4}\right|=\frac{7}{12}\)

a ) \(x+x\times\frac{1}{3}\div\frac{2}{9}+x\div\frac{2}{7}=252\)

\(x\times1+x\times\frac{1}{3}\div\frac{2}{9}+x\div\frac{2}{7}=252\)

\(x\times1+x\times\frac{1}{3}\times\frac{9}{2}+x\times\frac{7}{2}=252\)

\(x\times1+x\times\frac{9}{6}+x\times\frac{7}{2}=252\)

\(x\times\left(1+\frac{9}{6}+\frac{7}{2}\right)=252\)

\(x\times6=252\)

\(x=252\div6\)

\(x=42\)

b ) \(\left(3\times x-0,8\right)\div x+14,5=15\)

\(\left(3\times x-0,8\right)\div x=15-14,5\)

\(\left(3\times x-0,8\right)\div x=0,5\)

\(0,8\div x=3-0,5\)

\(0,8\div x=2,5\)

\(x=0,8\div2,5\)

\(x=0,32\)

\(\Leftrightarrow x+1,5x+3,5x=252\)

<=>6x=252

<=>x=42

ủng hộ nhe

thank you

\(1,\)\(x-\frac{3}{5}=\frac{3}{35}-\frac{-7}{6}\)

        \(x-\frac{3}{5}=\frac{3}{35}+\frac{7}{6}\)

        \(x-\frac{3}{5}=\frac{263}{210}\)

                    \(x=\frac{263}{210}+\frac{3}{5}\)

                    \(x=\frac{389}{210}\)

        VẬY: \(x=\frac{389}{210}\)

( 1/7 . x - 2/7 ) . ( -1.5 . x + 3/5 ) . ( 1/ 3 . x + 4/3) + 0

 <=> +) 1/7 . x - 2/7 = 0                                    +)    (- 1 / 5) . x +3/5 = 0                              +)  1/ 3 . x + 4/ 3 = 0

                    x = 2                                                                  x = 3                                                         x = 4

                                                    Vậy x = 2 : x = 3 ; x=4