=(x-1)(1-x)+x(x-1)²-x(x-1)³+.-x(x-1)²º¹¹+x(x-1)²º¹²
=-(x-1)²+x(x-1)²-x(x-1)³+.-x(x-1)²º¹¹+x(x-1)²º¹²
=(x-1)³-x(x-1)³+.-x(x-1)²º¹¹+x(x-1)²º¹²
=……
=(x-1)^2013