Verified answer

9 + √77                         9 + √77                                          9 + √77                 9 + √77
__________    =    _______________________ =   ______________ = __________   =
(√11 + √7)²              (√11)² + 2*√11*√7 + (√7)²            11 + 2√77 + 7          18 + 2√77

     9 + √77                     1

=  __________   =   ________

     2(9 + √77)                 2

ОТвет:  1/2.