Question

[Nguyễn Thế Kiên]

 Giúp mình với 

Answer 1

[Nguyễn Lê Phước Thịnh]

1: \(\dfrac{x}{5}=-\dfrac{12}{10}\)

=>\(\dfrac{x}{5}=-\dfrac{6}{5}\)

=>x=-6

2: \(\dfrac{-1}{3}=\dfrac{3}{x}\)

=>\(x=\dfrac{3\cdot3}{-1}=-9\)

3: \(\dfrac{-x}{-12}=\dfrac{9}{4}\)

=>\(\dfrac{x}{12}=\dfrac{9}{4}\)

=>\(\dfrac{x}{12}=\dfrac{27}{12}\)

=>x=27

4: \(\dfrac{8}{7}=\dfrac{16}{-x}\)

=>\(\dfrac{16}{-x}=\dfrac{16}{14}\)

=>-x=14

=>x=-14

5:

ĐKXĐ: x<>0

 \(\dfrac{3}{5}=-\dfrac{9}{x}\)

=>\(x=\dfrac{-5\cdot9}{3}=-5\cdot3=-15\)(nhận)

6: 

ĐKXĐ: x<>9

\(\dfrac{4}{5}=\dfrac{-12}{x-9}\)

=>\(x-9=\dfrac{5\cdot\left(-12\right)}{4}=\dfrac{-60}{4}=-15\)

=>x=-15+9=-6(nhận)

7: \(\dfrac{1}{6}=\dfrac{x+3}{18}\)

=>\(x+3=18\cdot\dfrac{1}{6}=3\)

=>x=3-3=0

8: ĐKXĐ: x<>7

\(\dfrac{x-7}{25}=\dfrac{9}{x-7}\)

=>\(\left(x-7\right)\left(x-7\right)=9\cdot25\)

=>\(\left(x-7\right)^2=15^2\)

=>\(\left[{}\begin{matrix}x-7=15\\x-7=-15\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=22\left(nhận\right)\\x=-8\left(nhận\right)\end{matrix}\right.\)

9: \(\dfrac{x}{6}=\dfrac{x-1}{5}\)

=>6(x-1)=5x

=>6x-6=5x

=>6x-5x=6

=>x=6

10: ĐKXĐ \(x\notin\left\{0;-1\right\}\)

\(\dfrac{1}{x+1}=\dfrac{2}{3x}\)

=>\(3x\cdot1=2\left(x+1\right)\)

=>3x=2x+2

=>3x-2x=2

=>x=2(nhận)