Question

" Os pontos A ( -3 , a) ,B ( 9 ,b ) e C (1 ,- 2 )sao colineares determine 2 a +b "

Answer 1

-3....a....1
9.....b.....1
1....-2.....1

-3b-18+a-b-9a-6 = 0
a-9a-3b-b=18+6
-8a-4b = 24 :(4)
-2a-b = 6 .(-1)
2a+b = -6

Answer 2

Olá, Brunori.

$\left[\begin{array}{ccc}-3&a&1\\9&b&1\\1&-2&1\end{array}\right] = 0$

$-3b+a-18-b-9a-6=0$
$-8a-4b-24=0$
$-2a-b-6=0$
$2a+b=-6$

$Resultado:-6$