因为ax2+（a+2）x+9a=0,有两个不相等的实数根x1、x2∴△=（a+2)^2-4*a*9a=a^2+4a+4-36a^2=-35a^2+4a+4=-35[(a-2/35)^2-4/35*35]+4=-35(a-2/35)^2+144/35＞0（a-2/35)^2＜144/35*35-12/35＜a-2/35＜12/35-2/7＜a＜2/5...