（4sqrt5-6sqrt7+2sqrt11）/（sqrt7-sqrt5)(sqrt11-sqrt7)

（4sqrt5-6sqrt7+2sqrt11）/（sqrt7-sqrt5)(sqrt11-sqrt7)
（4sqrt5-6sqrt7+2sqrt11）/（sqrt7-sqrt5)(sqrt11-sqrt7)

（4sqrt5-6sqrt7+2sqrt11）/（sqrt7-sqrt5)(sqrt11-sqrt7)
原式=（4√5-4√7-2√7+2√11）/（√7-√5）(√11-√7)
=[4(√5-√7)+2(√11-√7)]/（√7-√5）(√11-√7)
=-4/(√11-√7)+2/（√7-√5)
=-(√11+√7)+（√7+√5)
=√5-√11