-JzOOỌ 7(x+2008)<0 non
Jnoe >l f @+ 2oo8) | vh
l,f(x) l< J2009 vdi moi x e R k6o theo
I f @ +2008)(/(x) + Jzooql l< 2009 < 2010 , VxeR. TiI (2) suy ra (2) .f (* +2008)(/(x) +lDooql > -2010,vx e lR. o Ndu lm f c (0;+co) th) f (x +2008X/(x) + Jzoos)> 0 > -2ol 0, Vx e lR..
KÁt ludn. KhOng tdn tai hhm so th6a m6n didu ki6n bhi rạ O
(Nnan x6t. Dxy li đ to6n quen bi€i vd phuong tr'inh hhm trong 16p him li6n tuc n€n c6 nhidu ban giAi duoc vh da sd cdc ban đu giai dring, tuong tu nhu ciich di
trinh bIy 6 trcn. Ci6c ban sau day c6 ldi giai t6t: Bdc Ninh: Trdn Anh Tudh, 12A1, THPT Thu{n Thanh l;
VInh Phtic: Nguyin Munh QuAn,l lAl, THm chuy6n
Vinh Phrlc; Hi NOi: N guy|n Vdn Quy, 1 I A lT, Li Dinh Vrrqng, l0T, THm chuy6n DHKHTN Hn Ngi, N suvirt
Ddng HiÁu, 11T1, Trudng THPT Chuycn DHSP Hi
NQi; Hi Nam: N,gaydr Dftc Vinh,l2T, THfrf Chuy6n
Thinh; Thanh H6az Trinh Dang Son, I lT' THm
Chuy6n Lam Son; Ngh6 An: Nguvin Xtin Tltdng.
llAl, THFrI Chuydn Phan BQi Chlu, Ngrtyitt Vott
Hodng, 10T7, THPI Do Luong; Quing Ninh: GlrzriS
Tho Anh, Nguy€n Xudn Hdng, I lT THft Chuy6n Ha Long; Thila Thi6n - Hue; LA Thanh Philt ' l2T, THft
Qu6c hoc Hud; Quing Ngai: 7'a Dinh Dtttng, 1243,
THPT s6 l, Drlc Phd; Binh Dinh : L? Anh Trt, Nguvin Ngoc Quy, Nguyan DdngTiah, 1lT THP| Chuy€n LC
Qui Oon, Quy Nhon; Cdn Tho: L{ Dui Thiith' llAl
THPT Chuy6n Lf Tu Trqng; Phri YOn: Vr7 Vtin Huv,
llAl, THP| L,c Hting Phong, Tay Hda; Ddng Thr{p:
TOfiN t{O(
-2u2 +5u 1
-_l;
-u2 +2u +l
-2uz +5ưuz -2u-l
-u2 +2u +l
Trdn Minh D6, l2T, THPT Chuyen Nguy6n Dinh Chidu; D6ng Nai: Dr, Minh Ti4p, I lT, THIT Chuy€n
Bi6n Hda; Kon Tum: Coo Thanh Hcii, l2Al ,THW
Chuy6n Kon Tum; B6n Tre: Hujnh Cdng Bdng, l2T,
Khdng Hfru HiAp, I lT, THPT Chuyen Be*n Trẹ
NGUYEN VAN MAU
*Bni rflt397. cho đy sd (u,,) (n : t, z,...) duqc xac dinh nhtr sau ...) duqc xac dinh nhtr sau
Ll1 = ),1 , l.lrt = -2ul + 5u,,
, n =1r2,...
-ul +2u,, +1
Tim lim(u1 +u2 +...+ u,).
Ldi Sitiị Tru6c hdt ta c6 c6c nhAn x6t sau:
. -u2 +2ưl=2-(l-u)2 >0
e I - Jị, <t+Ji (l)
-2u2 +5u u(uz -4ư4) u(u-2)z
--uz
*2u*1'= -* *ru*1 = -uz +r;l>0
ncu 0<a <l+Ji,ư2.
Dnng kdt qui (3) suy m l < u6 < u1 < ug < ... -+ 2.
2) Cdc ban hqc sinh c6 ldi giii t6t:
Vinh Phric: Nguydn Dirc Anh, l0Al, Phnng Thi Tdm,