a) 5(x+3)-2x(3+x)=0

(x+3)(5-2x)=0

\(\left[{}\begin{matrix}x=-3\\x=\dfrac{5}{2}\end{matrix}\right.\)

b) 4x(x-2017)-x+2017=0

4x(x-2017)-(x-2017)=0

(x-2017)(4x-1)=0

\(\left[{}\begin{matrix}x=2017\\x=\dfrac{1}{4}\end{matrix}\right.\)

c) (x+1)² = x² + 1

x²+2x+1-x²-1=0

2x=0

Pt có vô số nghiệm