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Đề thi HSG Toán 9

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99ab cd eg+ + M
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deg 99abc M

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( 1)( 2)( 3)( 4) 1n n n n+ + + + +


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1 1 1 1

2 1 1 2 3 2 2 3 4 3 3 4 2025 2024 2024 2025
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2
1
x ay
ax y
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3a
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90EMD =
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d
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µ
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µ
0
0

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90
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·
·
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·
·
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^/
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·
0
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MA AN MN
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⇒ ≤

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";

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)
0 0
( ; )x y
6

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2 2 3
0 0
0 0
2 2 3
0 0 0 0
2 2 3
0 0
0 0
2 2 2 2 2 2 3 3 3
0 0 0 0 0 0
(*)(0,75 )
ac x bc y c
ax by c
bx cy a a bx a cy a
cx ay b

b cx ab y b
ac x bc y a bx a cy b cx ab y a b c d

+ =
+ =



+ = ⇔ + =
 
 
+ =
+ =


⇒ + + + + + = + +
KY

Z7"
2 2
0 0
0 0
2 2
0 0 0 0
2 2
0 0
0 0
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0 0 0 0 0 0
3 (**)(0,75 )

a bx ab y abc
ax by c
bx cy a b cx bc y abc
cx ay b
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ac x bc y a bx a cy b cx ab y abc d

+ =
+ =



+ = ⇔ + =
 
 
+ =
+ =


⇒ + + + + + =
bc'cc /
3 3 3
3a b c abc+ + =

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