Question

Os pontos A (3,1) , B (4, -2) e C (x,7) são colineares. Determine o valor de x.

Answer 1

$\left[\begin{array}{ccc}3&1&1\\4&-2&1\\x&7&1\end{array}\right]$ 
3 1  1    3 1
4 -2 1   4 -2
x  7  1   x  7

Det= -6+x+28+2x-21-4
3x=3
x=3/3
x=1