can someone help me in irrational number's pool 1

Question

anonymous · Answer

$$\sqrt{?} 81$$

anonymous · Answer

it said to simplify

anonymous · Answer

Is that negative 81?

anonymous · Answer

no it is positve $$\sqrt{81}$$

anonymous · Answer

Hmm, just confused because that wouldn't be an irrational number. The answer would just be 9 right?

anonymous · Answer

i think so  because it's one of the answers on the practice test

anonymous · Answer

my teacher give's us random test's do

anonymous · Answer

Oh, interesting. Well if it's just Square Root of 81 that's easy to explain! So if you are still having trouble with these what you need to ask yourself is what times itself will get you what's underneath the radical sign. 

For the example 81, 9*9 does equal 81. Rooting a number like this is the opposite of raising to a power!

anonymous · Answer

ohh okay thank you so much now i get it thanks for your help