Đặt \(\left(x^2-2x-3\right)^2=a\)
Sửa đề: \(9\left(x^2-2x-3\right)^4-37x\left(x^2-2x-3\right)^2+4x^2\)
\(=9a^2-37ax+4x^2\)
\(=9a^2-36\cdot ax-ax+4x^2\)
=9a(a-4x)-x(a-4x)
=(a-4x)(9a-x)
\(=\left\lbrack\left(x^2-2x-3\right)^2-4x\right\rbrack\left\lbrack9\left(x^2-2x-3\right)^2-x\right\rbrack\)