pls...answer

Let 3 be rational

then 3= a/b

3=a²/b²

3b²=a²

then 3 is a factor or a² and a  

let a=3c

3b²= 9c²

 b²=3c²

therefore 3 is a factor of b²and b

but this cannot take place since a and b dont have any common factor other than one

so our original assumption is wrong that 3 is rational

therefore  3 is irrational number.