Doubt Quant Exponent Problem

I had a problem with this question.
upon solving we get 21 * 21^1/2 = a * b^1/2

  1. After this greg writes the values of a and b as 21 and 21. Can we do that? Or is there a shortcut to this?

  2. And also aren’t we supposed to make “b” as small as possible?

Yes - this is just equating the two components essentially.

Can you make b any smaller while ensuring that a is an integer?

can you please show me how you equated it.

So we have

21 \times \sqrt{21} = a \times \sqrt{b}

Notice that when I put a = b = 21, I get the same thing as the LHS.