Question

5. (MVJ 2017) Qual a área do triângulo formado pelos pontos J(4, 3) R(2, 1) e M(5, 5)?

Answer 1

Calculando o determinante:

$\left|\begin{array}{ccc}4&3&1\\2&1&1\\5&5&1\end{array}\right| \left\begin{array}{ccc}4&3\\2&1\\5&5\end{array}\right| \\ \\ \\ D = 4 + 15 + 10 - 5 - 20 - 6 \\ \\ D = 29 - 31 \\ \\ D = -2$

Logo:

$A = \dfrac{|D|}{2} \\ \\ \\ A = \dfrac{|-2|}{2} \\ \\ \\ A = \dfrac{2}{2} = 1~u.a$