(17 + a)2 = 2209
First: divide both sides by 2 to get:
17 + a = 1104.5
Second: subtract 17 from both sides to get:
a = 1087.5
you can check for correctness by substituting the answer back into the original equation:
(17 + 1087.5)2 = 2209
(1104.5)2 = 2209
2209 = 2209