- IK+ MB M I= IK (dpcm) tr
2) Ngoli hai phuorg 6n tr6n mdt sd ban su dung cdc
phuong rin kh6c vi c0ng cho ldi girli dring: tinh toiin bang
luong gi6c; tinh toiin bang phuong phdp roa dQ; su dung phdp rrghich dio riim H phuorg rcn tU.nO=HB.HE
= trc.ttt,; sir dung dinh li Lyness md r6ng. 3) Xin ndu tin mot sd ban c6 ldi giii 16r:
Phri Tho: N grtyitr Tluitrlt Khuttg, I I Torin, THPT chuy€n
Hing Vuong. TP Viet Tr'i; Thrli Nguy6n: Vii Vcitt Htiu,
I 1A I, FrI Dan t6c NOi tni Thdi Nguydn, TP Th6i Nguy0n;VInh Phfc: Nguydn Mqnlt Quritr, DinhTilir Diing, llA,, VInh Phfc: Nguydn Mqnlt Quritr, DinhTilir Diing, llA,,
THPT chuyOn VInh Phric, TP. Phric YCn; Hi N6i: Nguyitt Vtin Linh, I lA, , Khdi THPT chuy€n DHKHTN, DHQG Hl N6i, Nguyirr Ngot. Sotr, I lT,, Truong TIJPT chuy€rr DHSP Hn NQi; Nghe An: Plulm lting Vrttttg, l0Ar, THft Phnn Drurg Luu, Y6n 'Ihinh, Dong Hint Trottg, I lAl, THtrt Quj,H-o.p 2, Ngrtv4ttTh0'Atilt, llT,,
THPI' chuy6n DH Vinh; Ben Tre: Khdng Hiar Hi?p,
llT, Hu)tit COng Bdng, l2T, THft chuydn Bdn Tre, TP
Bdrr Tre; Phri YOn: VdVon Ituy, llAl, THPT te Hdng Phong, Tiy Hda; TP Hd Chi Minh: Ngryht Lim Minh, TIIPT chuydn t € Hiing Phong.
NGUYEN MINH HA
*Bni T111389. Cho (,,,) ld m6t tld1, 5.,1
dtuntq. D(t 5,, = uii + ul + ul + ... + l/;1
r'6i ri : 1,2, ...
(iitt str tt,,11 S((.!, - l)trn + u,, ,)L, t'tii rrtoi
,t,,,
tt - 2.3,... Tim lirnlr,,.
Loi gitii. (Theo da sd cilc ban).
Tr) gii thidt ta c6 ngay S,, - S,-r : u?, > 0 , vdi n = 2,3,..., ta thu dugc ,S, ld mdt ddy tang.
VAy n6n, n6u d6y S, bi chan trOn thi ^S,, lh
m6t diy hdi tu vd lim a,] = lim($, - S,, r) = 0.
X6t trudng hqrp diy S,, kh6ng bi chln rren rhi
lim$, = aoP.
Tt gii thidt ta c6 Sn1ftn11 tu,, 1 5,,u,, +u,,-1 ,
vli n=2,3,....
Ttr ddy, ta thu du-o. c
S,u, + un-r 1 S2u2 * u1, vdi n = 2,3,... .
te ,rr,r-roro, T9!I#ff,
tt,,..r -.911/; *l/1
Dodti tt,,+2(-,
S,, S",
Srl/l * t/r
suY ra 0<tt,, a];j,n= 2.,5,."
k6o theo litn tt,, = 6.