determine whether each number or expression is rational or irrational. [also explain why/how they're rational/irrational]

negative square root of 1
3 and the square root of 2
square root of 15
-5 5/6
pi by 2nd power
2 and the square root of 9

i already know a couple of these are irrational, but i need the explanation part

-sqrt 1 = -1 this is an integer so it is rational
3sqrt(2); sqrt2 is not a perfect square so it is irrational
square root 15 is not a perfect square so it is irrational
- 5 5/6 is a rational number because it can be written in the form of a fraction with integer numerator and denominators -35/6.

pi^2 is irrational, pi is always irrational, it in non-terminating decimal
2sqrt 9 = 2 * 3 = 6 this is rational because 9 is a perfect square

Ithink the answer is a