Question

show that :(5+√5) (5-√5) is rational number

Answer 1

(5+√5) (5-√5)
⇒25-5√5+5√5-5
⇒20 is a rational number
⇒(5+√5) (5-√5) is rational number

Answer 2

by multiplying we get

( 5+√5)(5-√5)=

25-5=20
which is a rational number