Answer:
a) 
b) 
c) the points of the form (x, -x) for x≠0
Step-by-step explanation:
a)
If φ(x, y) = arctan (y/x), the vector field F = ∇φ would be
On one hand we have,
On the other hand,
So
b)
The domain of definition of F is
i.e., all the plane X-Y except the (0,0)
c)
Here we want to find all the points such that
where k is a real number other than 0.
But this means
So, all the points in the line y = -x except (0,0) are parallel to the vector field F, that is, the points (x, -x) with x≠ 0
The speed is the ratio between the distance and the time:

Data:
d=6343miles
t=9h

Then, the plane traveled at a speed of 704.77 miles per hour.
1.Simplify.
-2{x}^{2}-4x+13+12{x}^{2}+2x-25−2x2−4x+13+12x2+2x−25
2.Collect like terms.
(-2{x}^{2}+12{x}^{2})+(-4x+2x)+(13-25)(−2x2+12x2)+(−4x+2x)+(13−25)
3.Simplify.
10{x}^{2}-2x-1210x2−2x−12
Answer:
the answer is D
Step-by-step explanation:
(0, -3) , (1, -3) , (2, -3)
Hope this helps! :)
~Zane