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selenamalter

  • 3 years ago

Write the equation of the parabola in vertex form. A. y = (x + 1)2 + 3 B. y = (x + 1)2 – 3 C. y = (x – 1)2 – 3 D. y = (x – 1)2 + 3

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  1. selenamalter
    • 3 years ago
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    thats the wrong graph

  2. ZeHanz
    • 3 years ago
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    Do you see the zeroes at -1 and 4? The vertex is right in the middle of them: x = 1½. Also the y-coordinate of the vertex seems to be 7½. I cannot match it...

  3. selenamalter
    • 3 years ago
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    hold on let me get the other one

  4. ZeHanz
    • 3 years ago
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    Thought so... ;)

  5. selenamalter
    • 3 years ago
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  6. selenamalter
    • 3 years ago
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    there

  7. ZeHanz
    • 3 years ago
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    What are the coordinates of the vertex?

  8. selenamalter
    • 3 years ago
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    um, (1,3)

  9. selenamalter
    • 3 years ago
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    ?

  10. ZeHanz
    • 3 years ago
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    No, you have to go to the left and down... I get (-1, -3).

  11. selenamalter
    • 3 years ago
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    oh okay

  12. ZeHanz
    • 3 years ago
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    So if you look at the answer options, that doesn't help much: these same numbers are in every option, sometimes + sometimes -... You can find the right one by comparing this graph with that of the "father of all parabolas": y = x². That one has a vertex in (0, 0). So if x = 0, you get the other coodrinate of the vertex (also 0). In your parabola, you have to set x = -1 to get the vertex, so you get (x+1)² in the formula.

  13. selenamalter
    • 3 years ago
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    (x+1)^2+3

  14. ZeHanz
    • 3 years ago
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    That would be all, if the y-coordinate of the vertex was at y = 0, just as the vertex of y = x². But this isn't the case, it lies 3 units lower! OK, just subtract 3 from the formula, result: y = (x+1)²-3

  15. ZeHanz
    • 3 years ago
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    You added 3, which would make the parabola go 3 units up, instead of down...

  16. selenamalter
    • 3 years ago
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    okay, thank so much for all your help :D

  17. ZeHanz
    • 3 years ago
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    YW! Hope you understand the principle of moving the parabola.

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