Simplify $(2 \sqrt{392} - 21) + {(\sqrt{8} - 7)}^{2} = {(?)}^{2}$

A) 4	B) 5
C) 6	D) 9

Answer: C) 6

Explanation:

${(?)}^{2} = (2 \times 7 \sqrt{8} - 21 + 8 + 49 - 14 \sqrt{8}) = 57 - 21 = 36 = > ? = \pm 6$

Subject: Simplification
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Simplify 2392-21+8-72=?2