An imaginary number " i " is the squared root of -1, so whenever you square i it's like squaring a squared root. The squared root would cancel and you would be left with just the number under it, that is, the -1.
i ^ 2 = -1
Answer:

Step-by-step explanation:
Since there are 20 students, this will be the denominator.
Now, to find how many students have a dog and a cat, you need to subtract all the numbers with 20. The leftover number will be the amount of students.
7+8+8=23
23-20=3
So, there are 3 students who have a dog and a cat.
So, the fraction will be 
Dependency: A variable whose value depends on the value assigned to another variable (independent variable).
Correlation: The relationship between two or more variables is considered as correlation.
In statistics, when we talk about dependency, we are referring to any statistical relationship between two random variables or two sets of data. Correlation, on the other hand refers to any of a broad class of statistical relationships involving dependence.
If the 2 is little and on top of the a, then it's called "nine a squared."
As far as I know 0 IS a rational number. The only ones that are not rational are negative numbers. :) Though I could be wrong.....