Answer
$9\sqrt{7}$
Work Step by Step
Simplify each radical, when needed, to have:
$=4\sqrt{7}-\sqrt{4(7)} + \sqrt{49(7)}
\\=4\sqrt{7} -2\sqrt{7} + 7\sqrt{7}$
Combine like terms to have:
$=(4-2+7)\sqrt{7}
\\=9\sqrt{7}$
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