Using properties of determinants prove that:
[R1’ = R1 + R2 + R3]
[R1’ = R1/(x + 2a)]
[R2’ = R2 - R3]
[R2’ = R2/(x - a)]
= (x + 2a)(x - a)[x - ( - a) + ( - a - 0) + ( - a)] [expansion by first row]
= (x + 2a)(x - a)(x + a - a - a) = (x + 2a)(x - a)2
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