Question

(5-√5)(5+√5) examine whether the following number are rational or irrational

Answer 1

using identity (a+b) (a-b) we jave d value of dis as........ 5*2 - root 5 * 2
25 - 5
20 ..... and we know that 20 is rational

Answer 2

it is rational because
according to (a+b)( a-b)=a^2 - b^2
so the no. will be 5^2 -(√5)^2
= 25 - 5
= 20
and 20 is rational no.