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anonymous

  • 5 years ago

Why would f(1/4) be undefined?

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  1. Anikate
    • 5 years ago
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    well we no that the answer is f/4

  2. Anikate
    • 5 years ago
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    there is no equal sign

  3. asnaseer
    • 5 years ago
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    your question is not complete. you need to tel us what f(x) is defined to be.

  4. anonymous
    • 5 years ago
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    I have to explain why why f(1) = 3, f(0) = 2, and f(-1) = 1, but why f(1/4) is defined

  5. anonymous
    • 5 years ago
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    *undefined

  6. asnaseer
    • 5 years ago
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    have you been given the expression for f(x) in terms of x?

  7. anonymous
    • 5 years ago
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    in the 4x^2+ 7x - 2/ 4x-1

  8. asnaseer
    • 5 years ago
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    ok - now it makes sense

  9. anonymous
    • 5 years ago
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    i simplified it to x + 2/ 1 XD

  10. asnaseer
    • 5 years ago
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    if you look at the last term, you have a division by "4x-1". what will "4x-1" equate to when x=1/4?

  11. asnaseer
    • 5 years ago
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    \[f(x)=4x^2+7x-\frac{2}{4x-1}\]

  12. anonymous
    • 5 years ago
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    ohhh it would be 0

  13. asnaseer
    • 5 years ago
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    correct - so you would be dividing by zero - which is undefined.

  14. asnaseer
    • 5 years ago
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    BTW: your simplification to x + 2/ 1 is not correct.

  15. anonymous
    • 5 years ago
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    ahhhh :( what I do wrong?

  16. asnaseer
    • 5 years ago
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    can you please try and explain to me step by step what you did so that I can spot where you went wrong

  17. anonymous
    • 5 years ago
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    I factored to get (x+2)(4x-1)/4x-1 then canceled out common factors and got x+2/1

  18. asnaseer
    • 5 years ago
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    your factorisation in wrong. remember the last term is a fraction.

  19. asnaseer
    • 5 years ago
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    \[\begin{align} f(x)&=4x^2+7x-\frac{2}{4x-1}\\ &=\frac{(4x-1)(4x^2+7x)-2}{4x-1} \end{align}\]

  20. anonymous
    • 5 years ago
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    its supposed to be a rational expression o.O

  21. anonymous
    • 5 years ago
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    it looks like this : 4x^2+ 7x - 2 -------------- 4x-1

  22. asnaseer
    • 5 years ago
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    so the equation is supposed to be:\[f(x)=\frac{4x^2+7x-2}{4x-1}\]

  23. asnaseer
    • 5 years ago
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    which can be factored as:\[f(x)=\frac{(x+2)(4x-1)}{4x-1}\]

  24. anonymous
    • 5 years ago
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    yes :)

  25. asnaseer
    • 5 years ago
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    but you cannot cancel the 4x-1 because it would be like dividing top and bottom by zero when x=1/4

  26. anonymous
    • 5 years ago
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    i just canceled out common factors that what my teacher told me :(

  27. asnaseer
    • 5 years ago
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    you can only do that if you are told that x can NEVER be equal to 1/4

  28. asnaseer
    • 5 years ago
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    in this case I believe x can take on ay real value from minus infinity to plus infinity

  29. asnaseer
    • 5 years ago
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    and it is undefined at x=1/4

  30. asnaseer
    • 5 years ago
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    was the question asking you why is this undefined at x=1/4?

  31. anonymous
    • 5 years ago
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    yes

  32. asnaseer
    • 5 years ago
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    so then you can state that it undefined at x=1/4 because at x=1/4 we would be dividing by zero.

  33. anonymous
    • 5 years ago
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    okay Thank you!!! XD Wish i could giv you more than one medal o.O lol

  34. asnaseer
    • 5 years ago
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    You're welcome - I'm glad I was able to explain it well enough for you.

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