要使（x²+ax+1）（x四次方-6x三次方）展开式不含x四次方项,则a应等于?

要使（x²+ax+1）（x四次方-6x三次方）展开式不含x四次方项,则a应等于?
要使（x²+ax+1）（x四次方-6x三次方）展开式不含x四次方项,则a应等于?

要使（x²+ax+1）（x四次方-6x三次方）展开式不含x四次方项,则a应等于?
展开得 x^6 + (a-6)x^5 + (1-6a)^4 - 6x^3
由题意有 1 - 6a = 0
得 a = 1/6