Answer:
An equation of the circle with centre (-2,1) and radius 3 is 
Option D is correct.
Step-by-step explanation:
Looking at the figure we get centre of circle C (-2,1) and radius of circle r = 3
The equation of circle is of form:
where (h,k) is centre and r is radius.
We have centre C (-2,1) so, we have h = -2 and k = 1
We have radius = 3 so, r = 3
Putting values in the equation and finding the required equation:

So, an equation of the circle with centre (-2,1) and radius 3 is 
Option D is correct.
After putting the value of y from the second equation to the first equation, the resultant equation is
.
GIven:
The equations are:

It is required to put the value of y from second equation to the first equation.
<h3>How to solve equations?</h3>
The value of y from the second equation is,

Now, put this value of y in the first equation as,

Therefore, after putting the value of y from the second equation to the first equation, the resultant equation is
.
For more details about equations, refer to the link:
brainly.com/question/2263981
Answer: option d.
Step-by-step explanation:
If <em>y </em>varies directly as <em>x</em> and <em>z</em>, the form of the equation is:

Where<em> k</em> is the constant of variation.
If y=4 when x=6 and z=1 then substitute these values into the expression and solve for <em>k:</em>

<em> </em>Substitute the value of <em>k</em> into the expression. Then, the equation is:

To find the value of <em>y </em>when x=7 and z=4, you must substute these values into the equation. Therefore you obtain:


<em> </em>
Obtuse angle that’s the answer
Intersecting point 4,2 with slope of 1/2