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denise9423

  • 4 years ago

Can someone plz help me get started on these fractions f(x)=3x-8 div 4x+20

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  1. AsianDuck
    • 4 years ago
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    What do you need?

  2. saifoo.khan
    • 4 years ago
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    \[\frac{ 3x - 8}{4x + 20}\to \frac{3x-8}{4(x+5)}\]As there is nothing common between denominator and numerator so we cannot simply it.

  3. denise9423
    • 4 years ago
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    sorry I just found this.

  4. saifoo.khan
    • 4 years ago
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    No worries! :D

  5. denise9423
    • 4 years ago
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    How do I find the domain

  6. denise9423
    • 4 years ago
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    hi

  7. Akshay_Budhkar
    • 4 years ago
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    domain is all real numbers except for -5

  8. brinethery
    • 4 years ago
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    No division by zero. So what is x going to be when the denominator is zero?

  9. denise9423
    • 4 years ago
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    0

  10. saifoo.khan
    • 4 years ago
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    set the denominator equal to zero right? @Akshay_Budhkar

  11. brinethery
    • 4 years ago
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    no. x cannot = -5.

  12. Akshay_Budhkar
    • 4 years ago
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    Yes @sai

  13. Akshay_Budhkar
    • 4 years ago
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    @saifoo.khan

  14. denise9423
    • 4 years ago
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    f(x)=3x-8 over 4x+20

  15. brinethery
    • 4 years ago
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    @denise9423 Domain means all of the values x can take on. Here's your domain: \[x \neq-5\]

  16. Akshay_Budhkar
    • 4 years ago
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    If you have a look the function is having real values for all values except for x=5 when it is not defined as the denominator is zero

  17. denise9423
    • 4 years ago
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    can you show me how to get 5

  18. brinethery
    • 4 years ago
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    4x+20 =0 Solve for x. x=-5.

  19. brinethery
    • 4 years ago
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    Do you know why division by zero is not allowed?

  20. denise9423
    • 4 years ago
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    ok,then can i sub it also 3x-8

  21. brinethery
    • 4 years ago
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    no!

  22. brinethery
    • 4 years ago
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    you only need to worry about the bottom.

  23. denise9423
    • 4 years ago
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    no to ur question ok

  24. brinethery
    • 4 years ago
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    Remember this: What is 1 divided by 0? In other words, what times zero can equal 1? 0*2? 0*3? There is nothing you can multiply by zero to get 1. So whenever you get these fractions and they ask you to find the domain, just think about what x has to be in order for the denominator to equal zero.

  25. brinethery
    • 4 years ago
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    If you have an equation in the denominator, then set that equal to zero :-)

  26. brinethery
    • 4 years ago
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    *and solve for x.

  27. denise9423
    • 4 years ago
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    like this 4x+20=0

  28. brinethery
    • 4 years ago
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    Yup! :-)

  29. denise9423
    • 4 years ago
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    ok

  30. brinethery
    • 4 years ago
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    Or if you have 1/(x^2+2x+3) . If you have something weird like that, then set it equal to zero and use the quadratic formula to solve for your two x-values. Those x-values are what x can't equal. Sorry, I sound like I'm talking in riddles lol.

  31. denise9423
    • 4 years ago
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    ok so -7xyy over 28xxxxxy=0

  32. brinethery
    • 4 years ago
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    Are you in algebra?

  33. denise9423
    • 4 years ago
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    yes and Its rough

  34. brinethery
    • 4 years ago
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    I'm gonna be more specific with what I said, sorry my fault: Or if you have 1/(x^2+2x+3) . If you have something weird like that, then set it equal to zero and use the quadratic formula to solve for your two x-values. Those x-values are what x can't equal. Sorry, I sound like I'm talking in riddles lol. x^2+2x+3 = 0 (then use the quadratic formula and solve for x)

  35. brinethery
    • 4 years ago
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    That's okay!

  36. brinethery
    • 4 years ago
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    I don't think they'll ask you to find the domain of something with x's and y's. Or are they?

  37. denise9423
    • 4 years ago
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    yes

  38. denise9423
    • 4 years ago
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    no sorry

  39. denise9423
    • 4 years ago
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    simplify

  40. brinethery
    • 4 years ago
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    I can help you on something like that, but first off is that denominator stuff making sense? Really sleep on that and try to remember it b/c it's super important for calculus.

  41. denise9423
    • 4 years ago
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    -7xyy/28xxxxxy

  42. brinethery
    • 4 years ago
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    Okay well what multiples to 7 and 8 have in common? What can you divide them both by?

  43. brinethery
    • 4 years ago
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    I mean 28.

  44. denise9423
    • 4 years ago
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    yes it does bc it will help me remember to put=0 so I can solve for x

  45. brinethery
    • 4 years ago
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    good :-)

  46. denise9423
    • 4 years ago
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    4

  47. brinethery
    • 4 years ago
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    -7xyy/28xxxxxy You can divide the numerator and denominator by 7. Also, which has the smallest amount of x's, and then which one has the smallest amount of y's?

  48. denise9423
    • 4 years ago
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    3x7=28

  49. denise9423
    • 4 years ago
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    no 4x7=28

  50. brinethery
    • 4 years ago
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    The numerator has the smallest amount of x's. There is 1 of them. The denominator has the smallest amount of y's, which is 1 y. So we'll divide the numerator and denominator by 7. -1*x*y*y/4xxxxxy

  51. denise9423
    • 4 years ago
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    bottom has 5 x's and the top has 2 y's

  52. brinethery
    • 4 years ago
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    We have to cancel out the smallest amount of x's. And we also cancel out the smallest amount of y's. So we have: -1*y/4xxxx I canceled out an x on the top and bottom. Then I canceled out a y on the top and bottom.

  53. denise9423
    • 4 years ago
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    ok

  54. denise9423
    • 4 years ago
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    sorry i have a 911 gotta chk out b back later thank you for all ur help god bless

  55. brinethery
    • 4 years ago
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    k

  56. brinethery
    • 4 years ago
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    Anyway, -1*y/4xxxx can be re-written as: -y/4x^4 See Paul, my favorite math teacher: (I swear by his notes) http://tutorial.math.lamar.edu/Classes/Alg/IntegerExponents.aspx

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