(1) f(x)开口向上,(0,5)段在x轴下方,x=-1达到最大值.0,5是f(x)=0的根.f(x)=kx(x-5),f(-1)=12,k=2故f(x)=2x(x-5)=2x^2-10x(2)[2x^2+(a-10)x+5]/f(x)=[(2x^2-10x)+5+ax]/f(x)=1+(5+ax)/f(x)故(5+ax)/f(x)>0x不等于0,5...