Write the following sets in set builder form
(i) A={1,4,9,16,25,…..}
(ii) A={T,E,A,C,H,E,R}
(iii) A={1,-2}

Explanation

(i) A=P{x:x is the square of natual number}
or A={x:x= `n^(2)` where `n in N`}
(ii) A={x:x is a better of the word TEACHER{
(iii) The values of elements are 1,-2, Let the elements be i.e. x=1 and x=-2.
(x-1) (x+2)=0
`Rightarrow x^(2)+x-2=0`
So, A={x:x is solution of the equation `x^(2)+x-2=0}`