Question

3)determine o valor de x para que os pontos A(2,-3),B(x,7)eC(x,1)sejam colineares ​

Answer 1

$\Large\boxed{\begin{array}{l}\sf\begin{vmatrix}\sf2&\sf-3&\sf1\\\sf x&\sf7&\sf1\\\sf x&\sf1&\sf1\end{vmatrix}=0\\\sf 2\cdot(7-1)+3\cdot(x-x)+1\cdot(x-7x)=0\\\sf12-6x=0\\\sf 6x=12\\\sf x=\dfrac{12}{6}\\\\\sf x=2\end{array}}$