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10. 8/√3 +√7 = -2√3 +2√7
12. √5/√7-√5 = √35+5/2
17. If rectangle A is a golden rectangle then Rectangle B must be. If Rectangle B are squares of 8 and 15, then that would mean that the two sides of Rectangle B would be √64 + √225. Which √64=8 and √225=15. So yes Rectangle B is a golden rectangle.
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