Question

os pontos A(3.1), B(4,-2) e C(x,7) sao colineares determine o valor x

Answer 1

$\left|\begin{array}{ccc}3&1&1\\4&-2&1\\x&7&1\end{array}\right|=0\\ \\ -6+x+28+2x-4-21=0\\ \\ 3x=6-28+4+21\\ \\ 3x=3\\ \\ x=1$