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TwiztTiez

  • one year ago

Trapezoid WKLX has vertices W(2, −3), K(4, −3), L(5, −2), and X(1, −2). Trapezoid WKLX was reflected across the y-axis to produce trapezoid WꞌKꞌLꞌXꞌ. Which coordinates describe the vertices of the image? A. Wꞌ(2, 3), Kꞌ(4, 3), Lꞌ(5, 2), and Xꞌ(1, 2) B. Wꞌ(−2, −3), Kꞌ(−4, −3), Lꞌ(−5, −2), and Xꞌ(−1, −2) C. Wꞌ(−3, −2), Kꞌ(−3, −4), Lꞌ(−2, −5), and Xꞌ(−2, −1) D. Wꞌ(–3, 2), Kꞌ(4, –3), Lꞌ(–2, 5), and Xꞌ(–2, 1)

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  1. mathstudent55
    • one year ago
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    Let's look at a reflection across the y-axis. We start with point P with coordinates (a, b). |dw:1432767317600:dw|

  2. TwiztTiez
    • one year ago
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    Okay

  3. mathstudent55
    • one year ago
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    Notice that point P(a, b) becomes point P'(-a, b) after it is reflected across the y-axis. What change do you notice between (a, b) and (-a, b) ? |dw:1432767392230:dw|

  4. TwiztTiez
    • one year ago
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    Would It be D

  5. mathstudent55
    • one year ago
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    I haven't looked at he answers yet. I asked you a question. Answering it will help you understand this problem. In a reflection across the y-axis, a point with coordinates (a, b) becomes (-a, b). What difference do you see between (a, b) and (-a, b) ?

  6. TwiztTiez
    • one year ago
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    Ones negative the other is positive

  7. TwiztTiez
    • one year ago
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    @mathstudent55

  8. mathstudent55
    • one year ago
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    Yes, but a better way of describing it is: In the reflections, the x-coordinate changed signs. The y-coordinate remained the same. Do you see that?

  9. TwiztTiez
    • one year ago
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    Oh okay

  10. mathstudent55
    • one year ago
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    |dw:1432768112117:dw|

  11. mathstudent55
    • one year ago
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    Great. Now look at all the 4 given points. Look at each choice. The answer is the one that has all x-coordinates with just a sign change, but all y-coordinates remain the same.

  12. TwiztTiez
    • one year ago
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    So C?

  13. mathstudent55
    • one year ago
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    Let's look at just point W and point W' of choice C. W(2, -3) W'(-3, -2) Can you tell me what changed in the x- and y-coordinates between points W and W' of choice C?

  14. mathstudent55
    • one year ago
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    |dw:1432768399814:dw|

  15. mathstudent55
    • one year ago
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    |dw:1432768474614:dw|

  16. mathstudent55
    • one year ago
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    Both coordinates changed, and both changed more than just a sign change. Choice C cannot be the answer.

  17. TwiztTiez
    • one year ago
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    Oh okay well my other option is D

  18. TwiztTiez
    • one year ago
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    @mathstudent55

  19. mathstudent55
    • one year ago
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    We eliminated C. Why do you say your other option is D. There are three options besides C.

  20. TwiztTiez
    • one year ago
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    Well mainly from your description and it looks like the only one that makes sense

  21. mathstudent55
    • one year ago
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    Let's just look at point W. Original: \(W(\color{red}{2}, ~−3)\) Choice A: \(Wꞌ(\color{red}{2}, ~3)\) Choice B: \(Wꞌ(\color{red}{−2}, ~−3)\) Choice C: \(Wꞌ(\color{red}{−3}, ~−2)\) Choice D: \( Wꞌ(\color{red}{–3}, ~2)\)

  22. TwiztTiez
    • one year ago
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    OHHHHHHHHH

  23. TwiztTiez
    • one year ago
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    Okayy I get it

  24. mathstudent55
    • one year ago
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    I wrote above that a reflection over the y-axis will give you an x-coordinate that changes sign from the original x-coordinate. Above, all x-coordinates are in red. The original x-coordinate is 2. A change in sign means it must become -2. Do you see a choice in which the x-coordinate is -2?

  25. TwiztTiez
    • one year ago
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    B

  26. TwiztTiez
    • one year ago
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    @mathstudent55

  27. mathstudent55
    • one year ago
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    Exactly. Now notice that for all other points in choice B, the x-coordinate changes just the sign, and the y-coordinate remains the same.

  28. TwiztTiez
    • one year ago
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    Thanks so much!

  29. mathstudent55
    • one year ago
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    You're welcome.

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