... = (2; -3 ); u = ( -1 ; 4); u = (2; 0); u = (0; -1 ) r r r r b) u = (1; 3); u = (4; -1 ) ; u = (1; 0); u = (0; 0) r r Baứi Cho a = (1; -2 ), b = (0;3) Tỡm to ca cỏc vect sau: r r r r r r r 1r r r ... 11 Cho A(2; 3), B( -1 ; -1 ) , C(6; 0) a) Chng minh ba im A, B, C khụng thng hng b) Tỡm ta trng tõm G ca DABC c) Tỡm ta im D t giỏc ABCD l hỡnh bỡnh hnh Baứi 12 Cho A(0; 2) , B(6; 4) , C (1; -1 ) ... a) x = a + b ; y = a - b; z = a - 3b b) u = 3a - 2b ; v = + b; w = 4a - b r ổ 1 r r Baứi Cho a = (2; 0), b = ỗ -1 ; ữ , c = (4; -6 ) ố 2ứ r r r r a) Tỡm to ca vect d = a - 3b + 5c Trang Vect...