... AB CD d ( I1 , D ) = R12 = 16 - = , d ( I , D ) = R22 = 25 - 16 = 4 d ( I1 , D ) = d ( I , D ) = ị D / / I1I hoc i qua trung im cựa I1 I Tmax = + t c x = Do I1 I = < d ( I1 , D ) + d ( I , D ) ... ABCD) theo giao tuyn AB Do ú nu k SH ^ AB ti H thỡ SH ^ ( ABCD) SA2 + SB = AB = 4a D SAB vuụng S A D H B V (1,0 im) 0,25 2x N C 0,25 ti S ị SH = S BMDN M SA.SB a = AB = S ABCD - S AMD - SCND ... ỳng: (ac - bd ) a c + b d 2abcd (ab + cd )2 Ê a c + b d + a 2b + c d (ab + cd )2 Ê (a + b )(c + d ) (1) Du ng thc xy ac = bd 0,25 0,25 p dng (1) ta cú: [3( x 2) + ( y + 1)]2 10[( x 2) + (...