Formula:

Plug in 21 for a, plug in 72 for b.

Then you would get:

Then add 5184 and 441

Square root it.
and you'll get

I hope this helps
2 1/5
mutiply the whole number with the denominator
whole number =2
denominator=5
2*5=10
Add 10 with the numerator=1
10+1=11
Answer:
11/5