Explicație pas cu pas:
a) A(-7,9) ; B(3,-1)
[tex]x_{M} = \frac{ - 7 + 3}{2} = - \frac{4}{2} = - 2 \\ y_{M} = \frac{9 + ( - 1)}{2} = \frac{8}{2} = 4 [/tex]
[tex]M(x_{M} ;y_{M}) = M( - 2 ;4)[/tex]
b) A(-5,8), B(-12,8), C(4,-4)
[tex]AB = \sqrt{ {( - 5 - ( - 12))}^{2} + {(8 - 8)}^{2} } = \sqrt{ {7}^{2} } = 7[/tex]
[tex]AC = \sqrt{ {( - 5 - 4)}^{2} + {(8 - ( - 4))}^{2} } = \sqrt{ {9}^{2} + {12}^{2} } = 15 [/tex]
[tex]BC = \sqrt{ {( - 12 - 4)}^{2} + {(8 - ( - 4))}^{2}} = \sqrt{ {16}^{2} + {12}^{2} } = 20[/tex]
perimetrul ΔABC = 7 + 15 + 20 = 42
