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ganeshie8

  • one year ago

Find the y intercepts of \[\large y=\frac{3x^3-x}{x^2-4x}\]

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  1. campbell_st
    • one year ago
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    so for the y, intercept, don't you let x = 0 but factor out x 1st \[y = \frac{x(3x^2 - 1)}{x(x - 4)}\]

  2. ganeshie8
    • one year ago
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    Am i really allowed to let x = 0 here

  3. kanwal32
    • one year ago
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    3x^2-y(x-4)-1 and putting d>0

  4. campbell_st
    • one year ago
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    well if you factor out x you get \[y=\frac{3x^2 -1}{x - 4}\] and to find the y-intercept for any curve... its a case of letting x = 0 so \[y = \frac{3\times0^2 - 1}{0 - 4}\]

  5. ganeshie8
    • one year ago
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    don't we need to worry about the fact that x=0 is not part of the domain

  6. campbell_st
    • one year ago
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    x = 0 would be a point of discontinuity the way I read the question and work on the solution. lol... now I see your point...

  7. ganeshie8
    • one year ago
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    Haha mother wolfram also says (0, 1/4) is the y intercept http://www.wolframalpha.com/input/?i=y+intercepts+%283x%5E3-x%29%2F%28x%5E2-4x%29

  8. campbell_st
    • one year ago
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    here is my graph of the equation

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  9. ganeshie8
    • one year ago
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    It is a point discontinuity, should not be part of the domain

  10. campbell_st
    • one year ago
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    so then the curve doesn't have a y-intercept as its discontinuous at that point

  11. campbell_st
    • one year ago
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    I'm only in high school... so they may do other things at university

  12. ganeshie8
    • one year ago
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    Exactly! there should not be any y intercepts for this curve but idk what wolfram is thinking lol

  13. ganeshie8
    • one year ago
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    Your graphing calculator is correctly saying (0, 1/4) is a point discont

  14. campbell_st
    • one year ago
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    I'm in Australia and some people, I think from the US seem to not consider a point discontinuity anyway... glad you have a solution

  15. Anikate
    • one year ago
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    lol this is confusing, I'll just have my teacher explain it to me tomorrow

  16. anonymous
    • one year ago
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    Yet at the same time wolfram tells us the obvious domain http://www.wolframalpha.com/input/?i=domain+%283x^3-x%29%2F%28x^2-4x%29 Wolfram contradicts itself?

  17. anonymous
    • one year ago
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    I think after simplifying we can not let \(x=0\) and the graph of the function must be|dw:1434357482874:dw|

  18. ganeshie8
    • one year ago
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    then im convinced wolfram is lying about the y intercept

  19. jigglypuff314
    • one year ago
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    or perhaps some definition of a y intercept somewhere includes the limit?

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