Question

ifa=
$\frac{2 - \sqrt{5} }{2 + \sqrt{5} ?} and \: b = \frac{2 + \sqrt{5} }{2 - \sqrt{5} ?} find \: {a }^{2} - {b}^{2}$

Answer 1

rationalise a
(2-√5)^2/-1
=-(4+5-4√5)
rationalise b
(2+√5)^2/-1
=-(9+4√5)
a^2-b^2
=(9-4√5)^ 2-(9+4√5)^2
= -2(2(4√5)(9)