Help part 2
i need to know how do i do this
my teacher is really bad at explaining it

 Easy to illustrate, hard to explain!

#3  Center is  (0,-3) Radius is 2

Step-by-step explanation:

For any circle the basic formula is  

that means if you know the square root of the radius and you put that in for x, y has to be 0 or if you put it in for y, x has to be 0.

In #3, r^2 is 4, you know the square root is +2 or -2. That gives you the "x boundaries" for the graph. (The center will be half way between them, so 0)

When x is 2 you need y to equal 0, so figure y+3 =0, solve for y and that gives you y = -3.  So you have coordinates for the center of the circle: (0,-3)

 and the radius is the square root of the given 4 so the radius = 2  

The graph is attached below. Click on the thumbnail to expand properly!

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#4 is a bit more complicated, but if you think one step at a time, not impossible!

The square of the radius is 25, you know the square root  5, -5

Either x or y has to equal 5 when the other one is 0.

Use those facts to solve for x and y in parentheses.

x+4=5, so x= -4  and y-1=5  so y = 1  

Those give you your x and y coordinates for the center: (-4,1)

The radius is the square root of 25, so the radius is 5

The graph is below. Click on the attachment to expand properly!

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step-by-step explanation: