so crAo DUC c oAo rAo cA ur^Lu un rnr Hgc srNy cr6r voNG rixn LoP 9 THCS NAM HOC 2010-2011 on cHixn rntlc M6n thi: Toin Ngdy thi: 20 - 03 - 20ll Thdi gian: 150 phnit (Kh6ng ka thdi gian giao di) f\. \ lBni 1,.(4 di6m) \/ Tinh gi6tribii5u thric : I I i_______= Ld a = r/5 +zJe +ls-zJe 1r ri. 'Q) g = 12+ r/3 + 12-43 {Bni 2; G di€m) \'-'i u), ano'u + b + c: 0. Chtmg minh ring: a3 + b3 + c3 : 3abc b) Cho A-n(n+lXn+2{n+3). Chimg minh rdng v6i mgi n nguyOn duong thi A khdng ld sO chinh phuong. Biri 3: (a diem) a) Trong m[t phdng tea dQ Oxy cho dudng thdng (D). {Ap-4ighg6c t4o bdi dudng thang (O) "Oitru. b*, bitit <Iucrng thdng di qua di6m tffiAiilrn A(.6;-s) vd ee{;.f+-z). b) Cho da thric f(x) -1.2+2.3+3.4+ +x(x+l). Tim x AC f1x; : ll2. \ \nai +: 16 diom) \./ - Cho dudrng trdn (O), <tudng kinh AB. Ddy CD.vu6ng g6c voi AB tai E. Di6m M nim f@n cung nh6 BC cira dudng trdn (O), AM cit CD tai F. ' {-\ Qptt'i"g minh: AM ld phdn giSc cria g6c CMD. t'' \ ( Ullttug t6: AC2: AII.AIW /?r\ ( c))Gqi N ld giao di6m cria CB v6i AM; I ld giao di6m cria MD vcri AB. r , \"/r J rn nn Chtmg minh rdng: NI song song CD. Biri 5: (2 di6m) Cho tf giSc ABCD nQi ti6p duong trdn. Chtmg minh tittg : AB.CD + BC.AD: AC.BD . DUC c oAo rAo cA ur^Lu un rnr Hgc srNy cr6r voNG rixn LoP 9 THCS NAM HOC 2010 -2011 on cHixn rntlc M6n thi: Toin Ngdy thi: 20 - 03 - 20ll Thdi gian: 150 phnit (Kh6ng ka thdi. a3 + b3 + c3 : 3abc b) Cho A-n(n+lXn+2{n+3). Chimg minh rdng v6i mgi n nguyOn duong thi A khdng ld sO chinh phuong. Biri 3: (a diem) a) Trong m[t phdng tea dQ Oxy cho dudng