' ' ' 'ABC A B C A BCC B BCC B2 2 3TA CÓ

2

. ' ' '

.

' '

' '

ABC A B C

A BCC B

BCC B

2 2 3Ta có: ^{d M}

(

^{; (NPQ)}

)

^{=d A BCC B}

(

^{; ( ' ') .}

)

Đặt BC=x BB, '=y ta có S

_{BCC B}

_{' '}

=xy  + y y BN CP BC x

( )

^. 3 4 ^. 7+  = = = S xy

BCPN

2 2 241 1 2 4 4' . ' . .S

B NQ

= B N B Q= y x= xy

'

2 2 3 5 151 1 3 1 3S

C PQ

= C P C Q= y x= xy 2 2 4 5 40S xy xy xy xy xy S7 4 3 11 11⇒ = − − − = =

' '

NPQ

BCC B

24 15 40 30 301 11 11

( ) ( )

⇒ = = = ; ( ' ') . ; ( ' ') .V V d A BCC B S d A BCC B S

MNPQ

BCC B

BCC B

1

' '

' '

3 30 9011 ; ( ' ') .

( )

d A BCC B SV

BCC B

90 11.⇒ = =

1

3 1 45V d A BCC B S. ; ( ' ') .

2

2 3