\(4x\left(x-3\right)-2x\left(2x+5\right)=7\left(x-3\right)\)
\(\Leftrightarrow4x^2-12x-4x^2-10x=7x-21\)
\(\Leftrightarrow-29x=-21\)
\(\Leftrightarrow x=\dfrac{21}{29}\)
b) \(\left(x+2\right)\left(x-7\right)-2\left(x+3\right)=x\left(x+5\right)\)
\(\Leftrightarrow x^2-5x-14-2x-6=x^2+5x\)
\(\Leftrightarrow-5x-2x-5x=14+6\)
\(\Leftrightarrow-12x=20\Leftrightarrow x=\dfrac{-20}{12}=\dfrac{-5}{3}\)
\(a,4x^2-12x-4x^2-10x=7x-21\)
\(\rightarrow4x^2-4x^2-7x-12x=-21\)
\(\rightarrow-19x=-21\\ \rightarrow x=\dfrac{21}{19}\)
\(b,x^2-7x+2x-14-2x-6=x^2+5x\\ \rightarrow x^2-x^2-7x+2x-2x-5x=14+6\)
\(\rightarrow-12x=20\\ \rightarrow x=-\dfrac{5}{3}\)
