... 2t; -1 + t; -t ) ị MH = (2t - 1; t - 2; -t ) uuuu r r uuuu r r MH ^ uD 2(2t - 1) + (t - 2) - (-t ) = t = ị ud = MH = (1; -4 ; -2 ) ị d: ỡlog (3 x + y) + log5 (3 x - y ) = ợlog (3 x + y) - log3 ... = -1 ị B(1; 1), C(4; 1) ị AB ^ AC ị vuụng A 2) Gi s: A (-8 + 2t1 ;6 + t1;10 - t1 ) ẻ d1, B(t2 ;2 - t2 ; -4 + 2t2 ) ẻ d2 uuu r ị AB = (t2 - 2t1 + 8; -t2 - t1 - 4); 2t2 + t1 - 14) uuu r r ỡ-t - ... - 2), AC = (c - 3; -4 ) uuu uuu r r ỡ AB AC = ù ộ b = 5, c = ộ A(3; 2), B (-1 ; 5), C (0; -2 ) Ta cú: ị b = -1 , c = A(3; 2), B (-1 ; -1 ), C (6; -2 ) ùBC = 50 ợ Trn S Tựng uuuu r r 2) uD = (2;1; -1 )...