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

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

\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

Biri 5:
(2
di6m)
Cho tf
giSc
ABCD
nQi ti6p duong
trdn. Chtmg
minh tittg :
AB.CD
+
BC.AD:
AC.BD