中等MATH-GEOM-007
What is the radius of x^2 + y^2 + 2x − 4y − 4 = 0?
A. √5
B. 3✓ 答案
C. 9
D. 5
解說
Complete the square: (x + 1)^2 + (y − 2)^2 = 9, so the radius is 3. √5 drops the constant term. The value 9 is the square of the radius.
Complete the square: (x + 1)^2 + (y − 2)^2 = 9, so the radius is 3. √5 drops the constant term. The value 9 is the square of the radius.