Question

The beginning steps for determining the center and radius of a circle using the completing the square method are shown in the table.

Step 1
[original equation]: x2 + 8x + y2 − 6y = 11
Step 2
[group like terms]: (x2 + 8x) + (y2 − 6y) = 11
Step 3
[complete the square]:

Which of the following is the correct equation for Step 3? (1 point)
(x2 + 8x + 16) + (y2 − 6y − 9) = 11 + 16 − 9
(x2 + 8x + 16) + (y2 − 6y + 9) = 11 + 16 + 9
(x2 + 8x + 4) + (y2 − 6y − 3) = 11 + 4 − 3
(x2 + 8x + 4) + (y2 − 6y + 3) = 11 + 4 + 3

Answer 1

(b) (x^2 + 8x + 16) + (y^2 − 6y + 9) = 11 + 16 + 9

Explanation:

To complete the square of a binomial, the constant term of the perfect square trinomial is the square of half the coefficient of the linear term. It will always be positive.

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Answer Choices

a) 9 is subtracted, incorrectly

b) 16 and 9 are correctly added . . . this is the correct Step 3

c) half the linear term is added, incorrectly

d) the magnitude of half the linear term is added, incorrectly