a: \(\dfrac{2\left(3-7x\right)}{x+1}=\dfrac{1}{2}\)
=>4(3-7x)=x+1
=>-28x+12=x+1
=>-29x=-11
hay x=11/29
b: \(\dfrac{5x-1}{3x+2}=\dfrac{5x-7}{3x-1}\)
\(\Leftrightarrow\left(5x-7\right)\left(3x+2\right)=\left(5x-1\right)\left(3x-1\right)\)
\(\Leftrightarrow15x^2+10x-21x-14=15x^2-8x+1\)
\(\Leftrightarrow-11x-14=-8x+1\)
=>-3x=15
hay x=-5