Answer:
1. D
2. A
3. D
Explanation:
1.
To solve the equation
, we need to take "square root" of both the sides so we can isolate the variable "x".
Note: When taking square root, we need both positive(+) and negative(+) value as both positive & negative value's square is same.
Thus,

Answer choice D is right.
2.
So we need to take square root of both the sides to isolate the variable x and solve. Thus:

Now, we CANNOT TAKE THE SQUARE ROOT OF A NEGATIVE NUMBER. Hence, we cannot solve this. It is UNDEFINED.
Answer choice A is right.
3.
A square has an area given by
, where s is side length.
Equating the area to 79 and solving for s gives us the length of one side of the rug (remember to take square root of both sides to isolate s):

Note: we disregarded the negative value of -8.89 because length CANNOT BE NEGATIVE!
Hence, answer choice D is right.