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49(362601)1,():1f(x)=13x3-12ax2+(a-1)x+1(1,4),(6,+),a.2f(x)=12(a-1)x2+ax(1,3),a.3(2005,21())f(x)=lnx,g(x)=12ax2+bx,a0.b=2,h(x)=f(x)-g(x),a;4(2005,19)t0,P(t,0)f(x)=x3+axg(x)=bx2+c,P.()ta,b,c;()y=f(x)-g(x)(-1,3),t..2,.[1]:,y=f(x),f(x)0,f(x);f(x)0,f(x).,.f(x)=x3,,f(x)(-,+),f(x)=3x20.,,,.[1]:f(x)=0,f(x),0,.f(x)=0,f(x),f(x)=0,f(x).:f(x),(1)f(x)=0,f(x),f(x)0;f(x),f(x)0.(2)f(x)=0,f(x).:,.((),.)3:1f(x)=13x3-12ax2+(a-1)x+1(1,4),(6,+),a.f(x)=13x3-12ax2+(a-1)x+1,f(x)=x2-ax+a-1,20074610©1994-2008ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.(x)=13x3-12ax2+(a-1)x+1(1,4),(6,+),x(1,4),f(x)0,x(6,+),f(x)0,f(1)0f(4)0f(6)0f(1)=00f(4)=-3a+150,f(6)=-5a+3505a7,a(5,7).2f(x)=12(a-1)x2+ax(1,3),a.f(x)=12(a-1)x2+ax,f(x)=(a-1)x+a,f(x)=12(a-1)x2+ax(1,3),a=1,f(x)=10,f(x)(1,3);a1,f(x)=0x=a1-a,f(x)0(1,3),axx+1,x(1,3),a34(a1);,aa34.3(2005,21())f(x)=lnx,g(x)=12ax2+bx,a0.b=2,h(x)=f(x)-g(x),a;b=2,h(x)=lnx-12ax2-2x,h(x)=1x-ax-2=-ax2+2x-1x,h(x),h(x)0,x0,ax2+2x-10x0,a0,y=ax2+2x-1,ax2+2x-10x0;a0,y=ax2+2x-1,ax2+2x-10x0,=4+4a0,ax2+2x-1=0,=4+4a0,-2a0,,-1a0.,a(-1,0)(0,+).4(2005,19)t0,P(t,0)f(x)=x3+axg(x)=bx2+c,P.()ta,b,c;()y=f(x)-g(x)(-1,3),t.()a=-t2,b=t,c=-t3().()y=f(x)-g(x)=x3-t2x-tx2+t3,y=3x2-2tx-t2=(3x+t)(x-t)y=(3x+t)(x-t),y=f(x)-g(x)(-1,3),y=(3x+t)(x-t)0x(-1,3).y|x=-10,y|x=30.(-3+t)(-1-t)0,(9+t)(3-t)0.t-9t3.t(-,-9][3,+).1.().:,2006320074610©1994-2008ChinaAcademicJournalElectronicPublishingHouse.Allrightsreserved.