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korosh23

  • one year ago

Pre-calculus 12 question!

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  1. korosh23
    • one year ago
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  2. Vocaloid
    • one year ago
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    well, the height of the rectangle is given by the equation y = 9 - x^2 and the width is 2x

  3. korosh23
    • one year ago
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    Ok

  4. Vocaloid
    • one year ago
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    so area = ?

  5. korosh23
    • one year ago
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    I know how to get the area, but how do you know the height?

  6. korosh23
    • one year ago
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    @Vocaloid

  7. Vocaloid
    • one year ago
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    well, think of it this way: on the x-y coordinate plane, the x value tells you how far to the right or left to go, and the y-value tells you how far up or down to go, correct? since we want the height of the rectangle, it naturally follows that we want the y value

  8. korosh23
    • one year ago
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    yes correct

  9. Vocaloid
    • one year ago
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    so, we're given the equation y = 9 - x^2, so that's our height

  10. korosh23
    • one year ago
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    but the height of the rectangle is far smaller than the original prabola

  11. Vocaloid
    • one year ago
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    nope, not necessarily, remember that x is not a fixed value if we make x something super small, like 0.00001, then the height of the rectangle is almost the height of the parabola the point is that x changes

  12. korosh23
    • one year ago
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    ok I got this, and about the width, it looks like 4x to me. How is it 2x?

  13. Vocaloid
    • one year ago
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    well, think of it this way. let's try splitting the rectangle in half down the y-axis, like this: |dw:1440359170630:dw|

  14. korosh23
    • one year ago
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    Oh I see :) Yes and as we know negative value does not have any meaning in area.

  15. Vocaloid
    • one year ago
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    nope, that's not quite the point I was getting at...

  16. korosh23
    • one year ago
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    ok go ahead

  17. Vocaloid
    • one year ago
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    |dw:1440359429185:dw| would you agree that the distance marked is equal to x?

  18. korosh23
    • one year ago
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    yes

  19. Vocaloid
    • one year ago
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    so, all we have to do now is add the other half of the rectangle back in. |dw:1440359485663:dw|

  20. Vocaloid
    • one year ago
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    making our width equal to 2x

  21. korosh23
    • one year ago
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    oh I see

  22. Vocaloid
    • one year ago
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    any other questions?

  23. korosh23
    • one year ago
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    Everything is good. Thank you for clarifying this to me @Vocaloid

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