SOLUTION: 7. What is the standard equation of the circle with radius 5, and center (-5,-1)? A (x-5)^2 + (y-1)^2 = 25 B (x+5)^2 + (y+1)^2 = 25 C (x+5)^2 + (y+5)^2 = 5 D A circle canno

Question 162018: 7. What is the standard equation of the circle with radius 5, and center (-5,-1)?
A (x-5)^2 + (y-1)^2 = 25
B (x+5)^2 + (y+1)^2 = 25
C (x+5)^2 + (y+5)^2 = 5
D A circle cannot have a center at (-5,-1).
E (x-5)^2 - (y-1)^2 = 25
F (x+5)^2 - (y+1)^2 = 25

I used the formula for a circle and plugged the information in, and I got F for the right answer. But choice D is confusing me and i wanted to make sure F really is correct. Thank you!
Found 2 solutions by jim_thompson5910, scott8148:
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Since the center is (-5,-1) this means that h=-5 and k=-1. Remember, the center is at (h,k). Also, since the radius is 5, this tells us that r=5

Start with the general equation of any circle

Plug in , , and

Rewrite as . Rewrite as

Square 5 to get 25

So the standard equation of the circle with a radius of 5 and the center (-5,-1) is which means that the answer is B
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
for a circle of radius r, centered at (h,k); the general equation is
__ (x-h)^2 + (y-k)^2 = r^2

looks like B to me...
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