-2
fx＝ax2+x-a =a(x2+x/a+1/4a2)-1/4a-a=a(x+1/2a)2-(1+4a2)/4a∵有最大值17/8∴a<0当x=-1/2a时有最大值-(1+4a2)/4a=17/8-2(1+4a2)=17a-2-8a2=17a8a2+17a+2=0(8a+1)(a+2)=0a=-1/8 或a=-2
