... 2 2 2 1 1. ( 2 ) 2 2 2 21 1. 2 ( 2 )3 6 2 2MHCSMCH MCHx xAH AM cos HC AC AH a x xS MH MC a x xV SA S a a∆∆= = ⇒ = − = −⇒ = = −⇒ = = − O,5 Tõ biÓu thøc trªn ta cã: [ ]3 2 21 2 ... 0 ,25 VI .a 1 1Bpt ( ) ( )4 323 2 22 22 ≤−++⇔−−xxxx0 ,25 ( ))0( 32 2 2 >+=−ttxx BPTTT : 41≤+tt 2 4 1 0t t⇔ − + ≤ 323 2+≤≤−⇔t (tm)0 ,25 Khi ®ã : ( ) 323 2 32 2 2 +≤+≤−− xx 121 2 ≤−≤−⇔ ... 0 ,25 IV 1 1 .Ta có :VT = 2 2 2 ( ) ( ) a b c b c a A Bb c c a a b b c c a a b+ + + + + = ++ + + + + + 0 ,25 [ ]331 1 1 13 ( ) ( ) ( ) 2 1 1 1 1 93 ( )( )( )3 2 23 2 A a b b c c a a...