Why is the square root of a perfect square always rational

It is rational because when we solve a square root it gives us a positive and a negative value given that it is the square root of a perfect square  

Lets take an example 36 if we take the square root of 36 it would be 6*6

If a number is multiplied by itself then the product is said to be square of the number. And the number (i.e. 6) is called the square root

Perfect square number  

A number can be written as a product of two equal factors then the number is said to be a perfect square number

for finding the midpoint of any given 2 pair of points simply add the respective x coordinates with other x coordinate and the y coordinate with other y coordinate and divide them by 2

in your question it will be :

(3+1)/2 for the x coordinate of mid point i.e 2

[8+(-4)]/2 for the y coordinate of midpoint i.e 2

so coordinates of mid point of points (3,8) and (1,-4) will be (2,2)

the answer is d

the answer is in the first quadrant, which make the y-int positive.

since the dots are going down, therefore the correlation is negative

i hope it is right.