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.
Trang 1so crAo DUC c oAo rAo
cA ur^Lu un rnr Hgc srNy cr6r voNG rixn LoP 9 THCSNAM 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)
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Tinh gi6tribii5u thric :
I I i _=
Ld a = r/5 +zJe +ls-zJe
1 r r i
'Q) g = 12+ r/3 + 12-43 {Bni 2; G di€m)
\'-'i
u), anóu + 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)
"Oitrụ b*, bitit <Iucrng thdng di qua di6m tffiAiilrn Ặ6;-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.
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\nai +: 16 diom)
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- Cho dudrng trdn (O), <tudng kinh AB Ddy CD.vu6ng g6c voi AB tai Ẹ 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: AIỊAIW
/?r\
( c))Gqi N ld giao di6m cria CB v6i AM; I ld giao di6m cria MD vcri AB.
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