Solving binary linear equation x ^ 2 + 25x-123 = 0 I have no calculator

Solving binary linear equation x ^ 2 + 25x-123 = 0 I have no calculator

x^2+25x-123=0
x^2+25x+(12.5)^2=123+(12.5)^2
(x+12.5)^2=123+(12.5)^2
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