1.

Show that points`A (a , b + c)`, `B (b , c + a)`, `C (c , a + b)`are collinear.

Answer» Points A, B, C are collinear `hArr ar(triangleABC) =0`
Now, `ar(triangleABC) = (1)/(2) * |[a, a+b+c, 1],[b, a+b+c, 1],[c, a+b+c, 1]| [C_(2) to (C_(2) + C_(1))]`
` = (1)/(2)(a+b+c)*|[a, 1, 1],[b, 1, 1],[c, 1, 1]|`
`=(1)/(2)(a+b+c) xx 0 =0 [because C_(2) " and"C_(3) "are identical"]`
Hence, the given points are collinear.


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