f'(x)=x^2+2x+(2a-1)f'(x)=0在(1,3]上有解 =>f'(1)*f'(3)<=0且f'(1)<>0。=>(2+2a)(14+2a)<=0 且2+2a<>0=>-7<=a<-1
f'(x)=x^2+2x+(2a-1)f'(x)=0在(1,3]上有解即理解为抛物线x^2+2x+(2a-1)与x轴在(1,3]上有交点。f'(1)*f'(3)<=0且f'(1)>0(2+2a)(14+2a)<=0且2+2a>0解得-7<=a<-1