... 2,1trng,1vng: C6 C5C4 = 300 0,25 0,25 ã 1, 2trng,1vng: C6C5 C4 = 240 1 ã 1, 1trng,2vng: C6C5C4 =18 0 Theoquytccng,cỏchchnra4viờnbicúbamul: 300 + 240 + 18 0 =720 cỏch Doúscỏchchnra4viờnbikhụngcúbamul: 13 65 ... nờntacú b =1 hoc b =7 Vi b =1 tacú A(4 ;1) , B (0 ;1) Suyra: D 4) (4; Vi b =7 tacú A(-4; 7), B(0; - Suyra: D(- 4) 7) 4; uuuu r uuu r 8.b Gi M (1 + t; -1 - 2t ;1 + 3t ) ẻd Tacú: AM = ( -1 + t; -2 - ... = ( -1 + t; -2 - t;3t ), AB = ( -1; 0; -1) (1, 0im) uuuu uuu r r r r 1 uuuu uuu ộ AM , AB ự = (-2t - 2; 2t + 1; 2t + 2) ị S = ộ AM , AB ự = 12 t + 20t + AMB ỷ ỷ 2 1 3ử Dungthcxyrakhivchkhi t = -...