已知:(x2+ax+3)(x2-3x+b)计算结果不含x2及常数项,求a、b的值.

问题描述:

已知:(x2+ax+3)(x2-3x+b)计算结果不含x2及常数项,求a、b的值.

(x2+ax+3)(x2-3x+b)
=x4-3x3+bx2+ax3-3ax2+abx+3x2-9x+3b
=x4+(3a-3)x3+(b-3a+3)x2+(ab-9)x+3b,
∵计算结果不含x2及常数项,

b=0
b−3a+3=0

解得:
a=1
b=0