Question

Area  do triangulo,cujo vertices são (1,2) (3,4) (4 -1)

Answer 1

|1 2 1|
$\left[\begin{array}{ccc}1&2&1\\3&4&1\\4&-1&1\end{array}\right] =>$
([2.1.4]+[1.3.-1]+[1.4.1])-([-1.1.1]+[1.3.2]+[4.4.1]) => 
(8-3+4)-(-1+6+16) =>
(5+4)-(5+16)= 
9-21=-12
A=|D|/2
A=|-12|/2
A=12/2
A=6 u.m² //