bonsoir
A ( - 4 ; 1 )
B ( - 3 ; - 2 )
C ( 2 ; 1 )
( - 4 - 3 ) / 2 = - 7 /2 = - 3.5
( 1 - 2 ) / 2 = - 1 /2
M ( - 3.5 ; - 1/2 )
( - 3 + 2 ) / 2 = - 1 /2
( - 2 + 1 ) /2 = - 1 /2
N ( - 1/2 ; - 1/2 )
AC ² = ( 2 + 4 ) ² + ( 1 - 1 )² = 36
AC = √ 36 = 6
BC² = ( 2 + 3 )² + ( 1 + 2 )² = 5² + 3 ² = 25 + 9 = 34
BC = √34 ≅ 5.8