(√7+√5)(√7+√6)(√6-√5)
原式= 一一--------------------------------=(√7+√5)(√7+√6)(√6-√5)
(√7-√6)(√7+√6)(√6+√5)(√6-√5)
=7√6+√180+√210+√252-7√5-√150-√175-√210
=7√6+6√5+6√7-7√5-5√6-5√7
=2√6-√5+√7
(√7+√5)(√7+√6)(√6-√5)
原式= 一一--------------------------------=(√7+√5)(√7+√6)(√6-√5)
(√7-√6)(√7+√6)(√6+√5)(√6-√5)
=7√6+√180+√210+√252-7√5-√150-√175-√210
=7√6+6√5+6√7-7√5-5√6-5√7
=2√6-√5+√7