M(1 + T, – 1 + 2T, 1 – 3 T)  D. TA CÓ

2)M(1 + t, – 1 + 2t, 1 – 3 t)  d. Ta có:

MA + MB = ( t  2)

2

 (2 t  3)

2

 (2 3 )  t

2

+ (2  t )

2

 (2 t  3)

2

   ( 2 3 ) t

2

 

2

3

2

3

t t

14 ( 1) ( 1)

    

 

14 14

 

= 14 t

2

 28 t  17  14 t

2

 28 17 t =

3