Answer:
Which i think is the first one, there may just be a typing error.
Step-by-step explanation:
A polynomial of order n has the following format:

In which a is the leading coefficient,
are the roots.
If a root appears m times, they are said to have multiplicity m.
Leading coefficient of 1 and roots 21 and 31 with multiplicity 1

So the correct answer is:

Which i think is the first one, there may just be a typing error.
Answer:
It would probably be 15 actually
Hmm
let's try some numbers
we have 3 scenarios
x>y
x=y
x<y
x>y
x=-1 and y=-2
x-y=-1-(-2)=-1+2=1
it's positive when x>y
x=y
x=-1, y=-1
-1-(-1)=-1+1=0
nope
x<y
x=-2 and y=-1
-2-(-1)=-2+1=-1
nope
x-y is positive when 0>x>y
Given:-

To find:-
The simplified form.
At first we take conjucate and multiply below and above.
The conjucate is,

So now we multiply. we get,

Now we simplify. so we get,

We know the value of,

Substituting the value -1. we get,

So now we split the term to bring it into the form a+ib. so we get,

So the required solution is,