Respuesta :

hi

as Midpoint coordonates are  :  

M ( (X1+X2) /2   ;   ( Y1+Y2) /2 )

As X1 = -5

   X2 =  ?

   Y1 =  -4

   Y2 =  ?  

But we know the coordonates of  M,

we have :  

(- 5 + X2  ) / 2 =  -3

( -4 +Y2) /2 =  -4  

so :  

(- 5 + X2  ) / 2 =  -3

-5 + X2 = -6

         X2 =  -6 +5

         X2 =  -1  

( -4 +Y2) /2 =  2

  -4 + Y2 = 4

  Y2 =  4 +4

  Y2 =  8

So  point B   ( -1 ;8)