A vague doubt.( Big book 8)

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Am I lacking anything?
{correct annswer is A (only positive case.)}

In ETS land, avoid negative square roots when finding the roots of a number, they only take positive roots. However, if it was x2 = 64 then you would take x = 8 and -8. So option A is the correct answer.

Alternatively, notice that by squaring both sides you get 100 + 2 sqrt(59 * 41) and 100. So A is bigger.

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