Write the following in roster form
{x:x is a positive integer and x^2 <_ 100}

Solution:
Let A={x:x is a positive integer and x² $\le$ 100}
Now, in roster form,
A={1,2,3,4,5,6,7,8,9,10}

We know, positive integer is 1,2,3,4,5,6,7,8,9,10,...and so on.
1²=1
2²=4
3²=9
4²=16
5²=25
6²=36
7²=49
8²=64
9²=81
​​​​​​(10)²=100

So, A = {1,2,3,4,5,6,7,8,9,10}