... (1; -1) VI.a 0 ,25 0,5 0 ,25 0 ,25 ( ⇔ 2+ Bpt ( t = 2+ ) x2 − x ) x2 − x ( + 2 ) x2 − x BPTTT : (t > 0) 0 ,25 ≤4 0 ,25 t+ ≤4 t ⇔ t − 4t + ≤ ⇔ − ≤ t ≤ + (tm) ( Khi ®ã : − ≤ + ⇔ ) 0 ,25 x 2 x ≤ + ⇔ −1 ... to¹ ®é M’ 0 ,25 0 ,25 ( ;− ;− ) 3 ĐK: x>0 , y>0 VIb (1) ⇔ 22 log3 xy − 2log3 xy − = 0,5 0 ,25 x 2 (2) ⇔ log4(4x +4y ) = log4(2x +6xy) ⇔ x2+ 2y2 = ⇔log3xy = ⇔ xy = 3⇔y= Kết hợp (1), (2) ta nghiệm ... b+c c+a ⇒ A≥ a2 b2 c2 12 = (a + b + c) ≤ ( + + )(a + b + b + c + c + a) a+b b+c c+a ⇔ ≤ B .2 ⇔ B ≥ Tõ ®ã tacã VT ≥ + = = VP 2 0 ,25 0 ,25 0 ,25 0 ,25 DÊu ®¼ng thøc x¶y a=b=c=1/3 V.a 0 ,25 Ta cã: AB...