... 0.25 0.25 S trng hp cú th l C 11 = 16 5 Cỏc b (a, b, c) m a + b + c = 12 v a < b < c l (1, 2,9), (1, 3,8), (1, 4, 7), (1, 5, 6), (2,3, 7), (2, 4, 6), (3, 4,5) Vy P = 16 5 Trong khụng gian vi h ta ... x +1 x + + x +1 Do ( x + 3) + ( x ) = Nờn ta t 4t x + = 2sin = ; 1+ t2 2 (1 t ) x = cos = , 1+ t2 (*) 0.25 0.25 (1. 0 im) t = tan 7t + 12 t + vi , ú (*) m = 5t + 16 t + t [ 0 ;1] ... (2, 4, 16 ) cựng phng vi a = (1, 2, 8) , mp(P) cú PVT n = (2, 1, 1) uu r r Ta cú [ n ,a] = (6 ;15 ;3) cựng phng vi (2;5 ;1) 0.25 Phng trỡnh mp cha AB v vuụng gúc vi (P) l 2(x + 1) + 5(y 3) + 1( z +...