当p.q为何值时,(x²-5x+7)(x²+px+q)的展开式中不含x³和x²项.稍微具体一点的~
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当p.q为何值时,(x²-5x+7)(x²+px+q)的展开式中不含x³和x²项.稍微具体一点的~
当p.q为何值时,(x²-5x+7)(x²+px+q)的展开式中不含x³和x²项.
稍微具体一点的~
当p.q为何值时,(x²-5x+7)(x²+px+q)的展开式中不含x³和x²项.稍微具体一点的~
(x^2-5x+7)(x^2+px+q)=x^4+(p-5)x^3+(q-5p+7)x^2+(7p-5q)x+7q.
不含x^3和x^2项,则p-5=0、q-5p+7=0,解得:p=5、q=18.
p+(-5)=0
-5p+q+7=0