Question

If A(-1,1),B(1,3),&C(3,a) in three points AB=BC find the value 'a'.

Answer 1

${ (- 1 - 1)}^{2} + {(1 - 3)}^{2} = {(1 - 3)}^{2} + {(3 - a)}^{2} \\ 4 + 4 = 4 + {(3 - a)}^{2} \\ {(3 - a)}^{2} = 4 \\ 3 - a = 2 \: or \: 3 - a = - 2 \\ a = 1or5$