Question

Prove that 2√5 is national no

Answer 1

what ? I think u mean irrational no..

if yes here is your answer...

let 2√5 be a rational number
2√5 = a/b ,where a and b are integers and b is not equal to 0 ....

2√5= a/ b
= √5= a/2b

here a/2b is rational number

but √5 is irrational number
therefore, the contradiction we suppose is wrong
hence , 2√5 is irrational number

Answer 2

2 root 5 is never be rational number because root 5 is irrational and the product of irrational and rational number is always irrational.
Thank you. Hope this answer help you.