(x4- 2x3—3ax+1)(x3-2x2+x-b)
=x7-4x6+5x5-(b+2)x4+(2b+6a+1)x3-(3a+2)x2+(3ab+1)x-b
没有三次项和平方项则这两项的系数为0
所以2b+6a+1=0
3a+2=0
a=-2/3
b=(-6a-1)/2=3/2
(x4- 2x3—3ax+1)(x3-2x2+x-b)
=x7-4x6+5x5-(b+2)x4+(2b+6a+1)x3-(3a+2)x2+(3ab+1)x-b
没有三次项和平方项则这两项的系数为0
所以2b+6a+1=0
3a+2=0
a=-2/3
b=(-6a-1)/2=3/2