设另一个是:x^2+bx+k
(x^2+bx+k)(2x+1)
=2x^3+x^2+2bx^2+bx+2kx+k
=2x^3+(2b+1)x^2+(b+2k)x+k
对比有:
2b+1=-1
b+2k=-13
b=-1,k=-6
另一个是:x^2-x-6
2x^3-x^2-13x-6=(x^-x-6)(2x+1)
=(x-3)(x+2)(2x+1)
-13/2
-6
原式=x^2(2x+1)-x(2x+1)-6(2x+1)+6+k
=(2x+1)*(x^2-x-6)+6+k
=(2x+1)*(x-3)*(x+2)+6+k
所以 K=--6
2x^3-x^2-13x+k
=(2x+1)*x^2-2*x^2-13x+k
=(2x+1)*x^2-x*(2x+1)-12x+k
=(2x+1)*x^2-x*(2x+1)-6*(2x+1)+6+k
k=-6