Question

how is (5+√5)×(5−√5)a rational number?

Answer 1

Here is your answer it may help...

Answer 2

Hello!!!

(5+root5)(5-root5) is in the format of the identity'(a+b)(a-b)=a square - b square'.

So (5+ root5)(5-root5)=5square-root 5 square=25-5=20.

So,(5+ root5)(5-root5)=20 which is a rational number.
This is an example showing that the product of 2 irrational numbers is rational.

Thanks:)
#aditya