[問題]GWD13-06-Q4

[sayyes]

√[2√63 + 2/(8+3√7)] =

A. 8 + 3√7
B. 4 + 3√7
C. 8
D. 4
E. √7
Answer: D
有人願意告訴我解題方法嗎？

[kwtluck]

√[2√63 + 2/(8+3√7)]
=√{[2√9*7] + [2/(8+3√7)]*[(8-3√7)/(8-3√7)]}
=√{[2*3√7] + [2(8-3√7)]/[(8+3√7)(8-3√7)]}
=√[(6√7) + (16-6√7)/(64-63)]
=√[6√7+16-6√7]
=√16=4

[sayyes]

Thanks