(ax^2+bx+1)(2x^2-3x+1)
=2ax^4-3ax^3+ax^2+2bx^3-3bx^2+bx+2x^2-3x+1
=2x^4-(3a-2b)x^3+(a-3b+2)x^2+(b-3)x+1
因为不含一次项和三次项
所以b-3=0,b=3
3a-2b=0,a=2