\(\dfrac{-7}{x}=\dfrac{-21}{x-34}\)
\(\Rightarrow-7\left(x-34\right)=-21x\)
\(-7x+238=-21x\)
\(-7x+21x=-238\)
14x=-238
x=-17
đk : x khác 0 ; 34
\(-7x+238=-21x\Leftrightarrow14x=-238\Leftrightarrow x=-17\)(tm)
\(\Leftrightarrow\dfrac{-7\left(x-34\right)+21x}{x\left(x-34\right)}=0\\ \Leftrightarrow-7\left(x-34\right)+21x\\ \Leftrightarrow-7x+238+21x=0\\ \Leftrightarrow14x=-238\\ \Leftrightarrow x=-17\)
`(-7)/x = (-21)/(x-34)`
`=> -7 . (x-34) = x.-21`
`=> -7x - (-238) = -21x`
`=> -7x + 21x = -238`
`=> (-7 + 21)x = -238`
`=> 14x = -238`
`=> x = -238 : 14`
`=> x = -17`
