SOLUTION: x^2 + y^2 + 4x - 2y = -1 The equation of a circle in the xy-plane is shown above. What is the radius of the circle? A) 2 B) 3 C) 4 D) 9

Question 1046374: x^2 + y^2 + 4x - 2y = -1
The equation of a circle in the xy-plane is shown above. What is the radius of the circle?
A) 2
B) 3
C) 4
D) 9
Found 2 solutions by MathLover1, solver91311:
Answer by MathLover1(20850) (Show Source): You can put this solution on YOUR website!

The equation of a circle in standard form is:
....write it in standard form
.............complete squares

=>
so, your answer is: A)

Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

Rearrange:

Complete the square on x

Complete the square on y

Collect the constant terms in the RHS

The Right Hand Side is now the Radius SQUARED.

John

My calculator said it, I believe it, that settles it

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