Question

Sabendo que os pontos A (4, -1), B (1,7) e C ( 7, r) são colineares, determine o valor de r.

Answer 1

$\left[\begin{array}{ccc}4&-1&1\\1&7&1\\7&r&1\end{array}\right\left\begin{array}{ccc}4&-1\\1&7\\7&r\end{array}\right] = 0--\ \textgreater \ (28 -7 + r - 49 - 4r + 1) = 0;$ $--\ \textgreater \ -27 - 3r = 0--\ \textgreater \ - 3r= 27--\ \textgreater \ r = \frac{27}{-3} --\ \textgreater \ r = -9$