prove that (root of 2 + root of 5)2 is a irrational number.
let (root of 2 + root of 5 )2 be rational
2.root of 2 + 2. root of 5 = p by q ( where p & q are integers & not = to zero)
squaring on both sides
(2.root of 2 + 2. root of 5) 2 = (p by q)2
28 + 8 . root of 10 = p2 by q2
8. root of 10 =p2 - 28q2 by q2
root of 10 = p2 - 28q2 by 8q2
p2,-28q2,8q2 are rational
therefore p2-28q2 by 8q2 is rational
this contradicts our assumption
therefore (root of 2 + root of 5 )2 is irrational