\(\frac{8}{5}=\frac{-12}{x}\left(x\ne0\right)\)\(\Leftrightarrow8x=-60\)\(\Leftrightarrow x=\frac{-60}{8}=\frac{-15}{2}\)(tmđk)
\(\frac{x-1}{-4}=\frac{-4}{x-1}\left(x\ne1\right)\)\(\Leftrightarrow\left(x-1\right)^2=16\)\(\Leftrightarrow\orbr{\begin{cases}x-1=4\\x-1=-4\end{cases}\Leftrightarrow\orbr{\begin{cases}x=5\left(tm\right)\\x=-3\left(tm\right)\end{cases}}}\)
\(\frac{8}{5}=\frac{-12}{x}\)
\(\Rightarrow8x=-60\)
\(x=-60:8\)
\(x=-7,5\)
Vậy x=-7,5
\(\frac{x-1}{-4}=\frac{-4}{x-1}\)
\(\Rightarrow\left(x-1\right)^2=16\)
\(\left(x-1\right)^2=4^2\)
\(\Rightarrow\orbr{\begin{cases}x-1=4\\x-1=-4\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=4+1=5\\x=-4+1=-3\end{cases}}\)
vậy x=5 hoặc x=-3
Bài làm
a) 8/5 = -12/x
=> x = -12.5/8 = -7,5
Vậy x = -7,5
b) x-1/-4 = -4/x-1
=> ( x - 1 )( x - 1 ) = -4 . (-4)
=> x² - 2x + 1 = 16
=> x² - 2x + 1 - 16 = 0
=> x² - 2x - 15 = 0
=> x² - 5x + 3x - 15 = 0
=> x( x - 5 ) + 3( x - 5 ) = 0
=> ( x - 5 )( x + 3 ) = 0
=> x - 5 = 0 hoặc x + 3 = 0
=> x = 5 hoặc x = -3
Vậy x = 5 hoặc x = -3
c) -2/x = y/4
=> xy = -8
| x | 1 | -1 | 2 | -2 | 4 | -4 | 8 | -8 |
| y | 8 | -8 | 4 | -4 | 2 | -2 | 1 | -1 |
d) 4/y+2 = 7/3y+1
=> 4( 3y + 1 ) = 7( y + 2 )
=> 12y + 4 = 7y + 14
=> 5y = 10
=> y = 2
Vậy y = 2
e) 2x-1/3 = 3x+1/4
=> 4( 2x-1) = 3( 3x + 1 )
=> 8x - 4 = 9x + 3
=> -x = 7
=> x = -7
Vậy x = -7
