The point (x, y) is rotated 180 degrees counterclockwise about the origin. Write a rule to determine the coordinate of the image (x, y). Explain how you found the rule.

  (x, y) ⇒ (-x, -y)

Step-by-step explanation:

There are a couple of ways you can go at this.

1) Rotation by 180° in either direction is the same as reflection across the origin. That reflection is identical to reflection across both the x- and y-axes, in either order, so negates both coordinates. The transformation rule is ...

  (x, y) ⇒ (-x, -y)

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2) The rule for a general rotation by angle α is ...

  (x, y) ⇒ (x·cos(α) -y·sin(α), x·sin(α) +y·cos(α))

For α = 180°, sin(α) = 0 and cos(α) = -1. This makes the rule for rotation by 180° be ...

  (x, y) ⇒ (-x, -y)

3. (5x + 1) - (-10x + 6)

simplify the answer choice. combine like terms. remember to distribute the negative to the terms inside the second parenthesis. also remember that two negatives = one positive, and one of each sign = negative.

- (-10x + 6) = + 10x - 6

simplify. combine like terms:

5x + 1 + 10x - 6

5x + 10x + 1 - 6

15x - 5

∴ it is your answer

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