SUY RA A= (A+2B A) ( +2C) + (B+2A B) ( +2C) + (C+2A C) ( +2B) (0...
Câu 5Suy ra A=
(
a+2b a) (
+2c)
+(
b+2a b) (
+2c)
+(
c+2a c) (
+2b)
(0,5đ)2 2 2a b c+ + + ab+ bc+ ac Hay A ( a+ b+ c)2
=( 3)2
=3= = � = = =a b cSuy ra A =3 khi: 33 3+ + =a b c0.25
M = (
2 a+3 b−4 c)
2
= (
2 a+3 a−4 a)
2
=( a)2
=� �� �� �332
=13� �