(6x-1)(2x-1)(3x-1)(x-1)+x²
= [(6x-1)(x-1)][(2x-1)(3x-1)] + x²
= (6x²-7x+1)(6x²-5x+1) + x²
设6x²-6x+1=a
原式
=(a+x)(a-x)+x²
=a²-x²+x²
=a²
=(6x²-6x+1)²