中等math-u06-d02
The circle with equation (x - 1)^2 + (y + 2)^2 = 9 has centre and radius:
A. Centre (1, -2) with radius 3✓ 答案
B. Centre (-1, 2) with radius 9
C. Centre (1, 2) with radius 3
D. Centre (-1, -2) with radius 3
解說
The centre has the opposite signs of the bracket terms, so it is (1, -2). The radius is the square root of 9, which is 3, not 9.