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一道GMAT数学,求大侠解√[2√63 + 2/(8+3√7)] =

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一道GMAT数学,求大侠解√[2√63 + 2/(8+3√7)] =
√[2√63 +2/(8+3√7)] =
A.8 + 3√7
B.4 + 3√7
C.8
D.4
E.√7
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√[2√63 +2/(8+3√7)]
=√[2√9x7 +2/(8+3√7)]
=√[6√7 +2/(8+3√7)]
=√[6√7 +2(8-3√7)/(8+3√7)(8-3√7)]
=√[6√7 +2(8-3√7)/[8²-(3√7)²】
=√[6√7 +2(8-3√7)/64-63
=√[6√7 +2(8-3√7)
=√[6√7 +16-6√7)
=√16
=4