\(\frac{-5}{7}.\frac{2}{11}+\frac{-5}{7}.\frac{9}{11}\)                                    \(\frac{3}{5}.\frac{2}{8}+\frac{-6}{16}.\frac{2}{5}+\frac{-6}{15}:\left(-16\right)\)

\(=\frac{-5}{7}\left(\frac{2}{11}+\frac{9}{11}\right)\)                                 \(=\frac{3}{20}+\frac{-3}{20}+\frac{1}{40}\)

\(=\frac{-5}{7}.1=\frac{-5}{7}\)                                       \(=0+\frac{1}{40}=\frac{1}{40}\)

\(x-\frac{2}{5}=0,24\)                                           \(\left(\frac{7}{3}x-0,6\right):3\frac{2}{5}=1\)

\(\Rightarrow x=0,24+\frac{2}{5}=\frac{16}{25}\)                         \(\Rightarrow\left(\frac{7}{3}x-0,6\right):\frac{17}{5}=1\)

vậy x = 16/25                                                       \(\Rightarrow\frac{7}{3}x-0,6=\frac{17}{5}\)

                                                                          \(\Rightarrow\frac{7}{3}x=\frac{17}{5}+0,6=4\)

                                                                           \(\Rightarrow x=4:\frac{7}{3}=\frac{12}{7}\) 

                                                                           vậy x = 12/7

-3/5x = 27/5 + 7/3

-3/5x= 116/15

a) \(2\frac{1}{2}-\left(q-\frac{1}{2}\right)=\frac{3}{5}\)

\(\Rightarrow q-\frac{1}{2}=2\frac{1}{2}-\frac{3}{5}=\frac{19}{10}\)

\(\Rightarrow q=\frac{19}{10}+\frac{1}{2}=\frac{12}{5}=2,4\)

\(\Rightarrow q=2,4\)

b) \(\frac{1}{3}\cdot q-\frac{1}{5}\cdot q=0,6\)

\(=q\cdot\left(\frac{1}{3}-\frac{1}{5}\right)=0,6\)

\(=q\cdot\frac{2}{15}=0,6\)

\(\Rightarrow q=0,6:\frac{2}{15}=\frac{9}{2}=4,5\)

\(\Rightarrow q=4,5\)

c) \(\frac{3}{5}-q:\frac{1}{2}=\frac{1}{7}\)

\(\Rightarrow q:\frac{1}{2}=\frac{3}{5}-\frac{1}{7}=\frac{16}{35}\)

\(\Rightarrow q=\frac{16}{35}\cdot\frac{1}{2}=\frac{8}{35}\)

\(\Rightarrow q=\frac{5}{35}\)

Ở câu b áp dụng phân phối giữa phép nhân vs phép trừ.

a/ x= 3 hoặc x= -7

mới nghĩ ra có phần a thui ak thông cảm nhé

a. 9x² - 6x - 3 = 0

<=> 3(3x² - 2x - 1) = 0

<=> 3(3x² - 3x + x - 1) = 0

<=> \(3\left[3x\left(x-1\right)+\left(x-1\right)\right]=0\)

<=> 3(3x + 1)(x - 1) = 0

<=> \(\left[{}\begin{matrix}3x+1=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{3}\\x=1\end{matrix}\right.\)

b. (2x + 1)² - 4(x + 2)² = 9

<=> (2x + 1)² - \(\left[2\left(x+2\right)\right]^2=9\)

<=> (2x + 1 - 2x - 4)(2x + 1 + 2x + 4) = 9

<=> -3(4x + 5) = 9

<=> 4x + 5 = -3

<=> 5 + 3 = -4x

<=> -4x = 8

<=> -x = 2

<=> x = -2

a) \(\Leftrightarrow\left(9x^2-6x+1\right)-4=0\)

\(\Leftrightarrow\left(3x-1\right)^2-4=0\)

\(\Leftrightarrow3\left(x-1\right)\left(3x+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{1}{3}\end{matrix}\right.\)

b) \(\Leftrightarrow4x^2+4x+1-4x^2-16x-16=9\)

\(\Leftrightarrow12x=-24\Leftrightarrow x=-2\)

c) \(\Leftrightarrow3x^2-6x+3-3x^2+15x=21\)

\(\Leftrightarrow9x=18\Leftrightarrow x=2\)

d) \(\Leftrightarrow x^2+6x+9-x^2-4x+32=1\)

\(\Leftrightarrow2x=-40\Leftrightarrow x=-20\)

đây bạn

a)-12.(8)

b) -0.6

a) \(-0,6x-\dfrac{7}{3}=5,4\Leftrightarrow-\dfrac{3}{5}x=5,4+\dfrac{7}{3}\Leftrightarrow x=\dfrac{116}{15}.\left(-\dfrac{5}{3}\right)=-\dfrac{116}{9}\).

b) \(2,8:\left(\dfrac{1}{5}-3x\right)=1\dfrac{2}{5}\Leftrightarrow\dfrac{1}{5}-3x=2,8:\dfrac{7}{5}\Leftrightarrow-3x=2-\dfrac{1}{5}\Leftrightarrow x=\dfrac{9}{5}:\left(-3\right)=-\dfrac{3}{5}\).