Find the radius of the circle x^2+y^2+2x+4y-31 = 0.
Answer and explanation
Correct answer: A. 6
- Step 1: Complete the square: (x + 1)^2 + (y + 2)^2 = 36.
- Step 2: The radius is the square root of 36, which is 6.
Answer
6.
Why not the others: '36' reports r^2 instead of r; '31' uses the constant term as the radius; '7' adds one in completing the square.
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