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Bananas1234

  • one year ago

Where is the vertex of the parabola? y = x2 + 2x – 3 Above the x-axis Below the x-axis On the x-axis On the y-axis

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  1. JoannaBlackwelder
    • one year ago
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    The x coordinate of the vertex can be found by using the formula -b/2a for a quadratic in standard form.

  2. JoannaBlackwelder
    • one year ago
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    And the y coordinate from substituting that value back in for x and solving for y.

  3. JoannaBlackwelder
    • one year ago
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    So, what do you get for the x coordinate of the vertex?

  4. Bananas1234
    • one year ago
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    i am stil not sure @JoannaBlackwelder

  5. JoannaBlackwelder
    • one year ago
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    Can you identify a, b, and c?

  6. Bananas1234
    • one year ago
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    no

  7. JoannaBlackwelder
    • one year ago
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    ax^2 + bx + c

  8. JoannaBlackwelder
    • one year ago
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    So, a is 1, b is 2, and c is -3

  9. JoannaBlackwelder
    • one year ago
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    Do you see how I got those numbers?

  10. Bananas1234
    • one year ago
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    i think so

  11. JoannaBlackwelder
    • one year ago
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    They are the coefficients of each term in the quadratic.

  12. JoannaBlackwelder
    • one year ago
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    So, can you try to plug those numbers into the formula I gave?

  13. Bananas1234
    • one year ago
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    ax^2 + bx + c = 1x^2 + 2x + -3

  14. JoannaBlackwelder
    • one year ago
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    So, that is the expression given in the problem. Do you see how that is the same?

  15. JoannaBlackwelder
    • one year ago
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    The formula I was meaning is the -b/2a for the x coordinate of the vertex.

  16. Bananas1234
    • one year ago
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    -2/2^1

  17. JoannaBlackwelder
    • one year ago
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    Close, -2/2*1

  18. JoannaBlackwelder
    • one year ago
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    So, that simplifies to -1

  19. JoannaBlackwelder
    • one year ago
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    And that is the x coordinate of the vertex. :-)

  20. Bananas1234
    • one year ago
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    ok

  21. JoannaBlackwelder
    • one year ago
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    Now we need to find the y coordinate to find the specific point.

  22. JoannaBlackwelder
    • one year ago
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    We do that by subbing in the -1 into x into the expression.

  23. JoannaBlackwelder
    • one year ago
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    (-1)^2 + 2(-1) - 3

  24. JoannaBlackwelder
    • one year ago
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    See how I did that?

  25. Bananas1234
    • one year ago
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    yes

  26. JoannaBlackwelder
    • one year ago
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    :-) So, what does that simplify to?

  27. Bananas1234
    • one year ago
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    -4

  28. JoannaBlackwelder
    • one year ago
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    Right! So, what is the coordinate of the vertex?

  29. Bananas1234
    • one year ago
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    -1,-4

  30. JoannaBlackwelder
    • one year ago
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    Sweet. So, is that above, below, or on the axes?

  31. Bananas1234
    • one year ago
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    below

  32. JoannaBlackwelder
    • one year ago
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    :-)

  33. Bananas1234
    • one year ago
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    Thanks so much!

  34. JoannaBlackwelder
    • one year ago
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    You're welcome!

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