O valor de x para que os pontos A = (x, 2), B = (3,1)e C = (-4,2) sejam alinhados
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O determinante formado pelas coordenadas dos 3 pontos tem que ser igual a zero.
![\left[\begin{array}{ccc}x&2&1\\3&1&1\\-4&2&1\end{array}\right] \left[\begin{array}{ccc}x&2\\3&1\\-4&2\end{array}\right] =0 \\ x-8+6-6-2x+4=0 \\ -x-4=0 \\ x=-4](https://tex.z-dn.net/?f=++%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7Dx%26amp%3B2%26amp%3B1%5C%5C3%26amp%3B1%26amp%3B1%5C%5C-4%26amp%3B2%26amp%3B1%5Cend%7Barray%7D%5Cright%5D+++%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7Dx%26amp%3B2%5C%5C3%26amp%3B1%5C%5C-4%26amp%3B2%5Cend%7Barray%7D%5Cright%5D+%3D0++%5C%5C+x-8%2B6-6-2x%2B4%3D0+%5C%5C+-x-4%3D0+%5C%5C+x%3D-4 "\left[\begin{array}{ccc}x&2&1\\3&1&1\\-4&2&1\end{array}\right] \left[\begin{array}{ccc}x&2\\3&1\\-4&2\end{array}\right] =0 \\ x-8+6-6-2x+4=0 \\ -x-4=0 \\ x=-4")
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