... + + =6 86 84 82 x − 214 x − 132 x − 54 ⇔ ( − 1) + ( − 2) + ( − 3) = 86 84 82 x − 300 x − 300 x − 300 ⇔ + + =0 86 84 82 1 ⇔ (x-300) + + = ⇔ x-300=0 ⇔ x=300 VËy S = { 300} 86 84 82 a, ... ( a + ) + 15 ( =(a =(a =(a )( ) = a + 8a + a + 8a + 15 + 15 ) ( ) + 8a + 22 a + 8a + 120 ) + 8a + 12 ) ( a = ( a + 2) ( a + 6) ( a 2đ 2 + 8a + 11 − 2 ) + 8a + 10 ) ⇔ x − ( a + 10 ) x + 10a + = ... đề thi HSG Tốn Năm học: 2011-2012 xy=2(x+y+x+y-4) xy-4x-4y= -8 (x-4)(y-4) =8= 1 .8= 2.4 0,25 Tõ ®ã ta t×m ®ỵc c¸c gi¸ trÞ cđa x , y , z lµ : (x=5,y=12,z=13) ; (x=12,y=5,z=13) ; (x=6,y =8, z=10) ; (x =8, y=6,z=10)...