Which of the following fractions is equal to 1√5−√7?
−(√5+√7)4
−(√5+√7)2
−(√5−√7)2
−(√5+√7)8
Rationalizing the expression we get, 1√5−√7=√5+√7(√5−√7)(√5+√7)
=√5+√7(√5)2−(√7)2
=√5+√75−7 =−(√5+√7)2
Which of the following fraction is equal to 1√5−√7?