De thi dai hoc nam 2013 lan 2 mon Toan cua Nhat Ban (De 1)

1

1

2
x2

yD

a >0
DE

a D

7
˙

q

x D

B

A
x

F

x
aD

ax C 3

2 y

3

G

1

. 3;

5/


H

2

I
L

K

0 3

p

q

H

p

q

J

J
R

x y

p q r
.x C y/2 D a.x 2 C y 2 / C bxy

p: x y

a b
q: x D 0

yD0

r: x D 0

yD0

p
p

r

p
p
p

r

aDbD1

I

aDbD2

K

aD2
xC

p
L

b

y

M
p

!2

0

B
C@

b
N

O
P

q

Á2 1

C 2
Ay D 0
b

Q


0
1
2
3

2

R


1

1

3

5

5

3

9

2
*1

1

2

B

A

CD

E

6

F
*2

GH
I

*1
*2

trial
expected value

3


n D x2

n

2

nDx

3

x

n

x

n

2
n

n

13

n

n

61

n D x2

x
y

(i)

x 2 C 13 D y 2
x

y

xD
nD

M

J

xD

yCx D

KL

N

yD

OP

n D x3

x

x 3 C 61 D y 3

xD
n

Q

yD

ST

4

R

x


a

2
x2

x

a

A

2.a C 2/x C 25 > 0

Á2

a2

B

aC

x
EF

>
xD

1


G


K

x
HIJ

5

CD


A

AB D 4 AC D 5 cos †BAC D

1
8

†BAD D †ACB †CAE D †ABC

4ABC

BCD

AB

q

C

D

E

4ACE

S1 S2
F

S W S1 W S2 D 1 W

4ADE

E

S

SD

4ABD

B

G

W

q

N

T

T D
DED

LM

OP

Q
R

6

HI
JK

D

C