Question

determine a area do triangulo de vertices a(-1,2) B (3,1) C (2,0)​

Answer 1

M= [-1 2 1]

[3 1 1]

[2 0 1]

Det M=-1(1)-2(3-2)+1(-2) =-1-2-2=-5

$A=\frac{1}{2}.|DetM| \\ A=\frac{1}{2}.|-5| \\ A=\frac{1}{2}.5 \\ A=\frac{5}{2} u.a$