Question

Prove that (2+root 5) (2-root 5) is irrational no.

Answer 1

Solution:

(2+√5)(2-√5)

= 2² -(√5)²

/* (a+b)(a-b)=a²-b² */

= 4 - 5

= -1 [ Rational number ]

Therefore,

(2+√5)(2-√5) is a rational number.

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Answer 2

it is a rational number hope you understand:-