can someone help me find the radius of the circle

Question

What is the radius of the circle 2x² + 2y²− 8x + 12y+ 15 = 0 ?

I'd really appreciate the help I get the square root of 11/2 but the answer says it's wrong?

Answer 1

2x²-8x + 2y²+12y +15 = 0

2(x²-4x) + 2(y²+6y) +15 =0

2(x²-4x) + 2(y²+6y) = -15

Divide by 2:

(x²-4x) + (y²+6y) = -7.5

Complete the square:

(x²-4x+4) + (y²+6y+9) = -7.5 +4 +9

(X-2)² + (y+3)² = 5.5

Radius = (5.5)^0.5

Answer 2

2x² - 8x + 2y² + 12y + 15 = 0

2x² - 8x + 2y² + 12y = -15

2(x² - 4x + 4) + 2(y² + 6y + 9) = - 15 + 8 + 9

2(x - 2)² + 2(y + 3)² = 2

(x - 2)² + (y + 3)² = 1