a) \(2x^2+3\left(x-1\right)\left(x+1\right)=5x\left(5-1\right)\)
\(\Leftrightarrow2x^2+3\left(x-1\right)\left(x+1\right)-5x\left(5-1\right)=0\)
\(\Leftrightarrow2x^2+3\left(x^2-1\right)-5x.4=0\)
\(\Leftrightarrow2x^2+3x^2-3-20x=0\)
\(\Leftrightarrow5x^2-20x-3=0\)
\(\Leftrightarrow x=4,144761059\)