a)
\(\left(2x-5\right)^2-4x\left(x-3\right)=0\\ 4x^2-20x+25-4x^2+12x=0\\ 4x^2-4x^2-20x+12x+25=0\\ -8x+25=0\\ -8x=-25\\ x=\dfrac{25}{8}\)
b)
\(3x\left(x+5\right)-2x-10=0\\ 3x\left(x+5\right)-2\left(x+5\right)=0\\ \left(x+5\right)\left(3x-2\right)=0\\ \left[{}\begin{matrix}x+5=0\\3x-2=0\end{matrix}\right.\left[{}\begin{matrix}x=-5\\x=\dfrac{2}{3}\end{matrix}\right.\)