m = 3p - ½n

p ( - 1 ; 2 )

3p = ( 3 × (-1) ; 3 × 2 ) = ( - 3 ; 6 )

n ( 6 ; - 8 )

- ½n = ( -½ × 6 ; -½ × (-8) ) = ( - 3 ; 4 )

m = ( - 3 - 3 ; 6 + 4 ) = ( - 6 ; 10 )