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kdarnell08

  • one year ago

4x^2+81-36x

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  1. tkcena75
    • one year ago
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    (2x-9)^2

  2. kdarnell08
    • one year ago
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    can ya go through the steps for me?

  3. tcarroll010
    • one year ago
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    There are a couple of ways to do this. The quickest is factoring, if you are good at seeing factors. This is a little tricky with factoring, so when in doubt you can always use the quadratic formula (the second way) which is actually my favorite way.\[x = \frac{ -b \pm \sqrt{b ^{2} - 4ac} }{ 2a }\]where you have an equation in the form: ax^2 + bx + c = 0 So you have a=4, b=-36, and c=81 So, you substitute those into the formula.

  4. kdarnell08
    • one year ago
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    ughh i just dont understand this!!

  5. tcarroll010
    • one year ago
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    Well, let's look at factoring for a bit instead. As for factoring (the other way), you can rewrite the equation into: (2x)^2 - 36x + 9^2 You will see that the first term is a square and the third term is a square which might sugeest that the factors are squared.

  6. tcarroll010
    • one year ago
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    That means that we can partially set up the solution: (2x )(2x ) But the third term is a square also, so going a bit further and just leaving out the signs: (2x 9)(2x 9) Now this all presupposes you can work the distributive law well enough: (a + b)(c + d) = a(c + d) + b(c + d) = ac + ad + bc + bd Tell me before we go any further, can you deal with that last equation?

  7. kdarnell08
    • one year ago
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    yes.

  8. tcarroll010
    • one year ago
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    That's great! That really is. Don't worry if it's a little rocky. You're not supposed to "see it all" right away, so we'll just go along until it gets murky for you. np. So, continuing where we left off with the factoring, writing it again: (2x 9)(2x 9) We have a good start, but we don't have signs yet. We know that 81 is positive so the signs are both negative or both positive. Since the 36x has a negative sign, we go with negative signs: (2x - 9)(2x - 9)

  9. tcarroll010
    • one year ago
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    Now, we are goingto multiply this out to check our work: (2x)(2x - 9) - 9(2x - 9) = 4x^2 - 18x - 18x + 81 = 4x^2 - 36x + 81

  10. tcarroll010
    • one year ago
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    So, that's the same as our original expression with a slight change in order of the terms. So, that's 2 ways to do this. Ok, your turn, ask questions.

  11. kdarnell08
    • one year ago
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    ok. i understand most of it i just dont understand what happened to the #36

  12. tcarroll010
    • one year ago
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    In the checking of the solution that I did, the -36x came from the -18x -18x

  13. kdarnell08
    • one year ago
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    i get it!!!!!

  14. tcarroll010
    • one year ago
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    Believe me. If really get this or most of it, or even half. That's real progress! For anyone! I suggest going over this a couple times to consolidate your understanding

  15. tcarroll010
    • one year ago
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    And don't give up on the quadratic formula because that is actually much more important.

  16. kdarnell08
    • one year ago
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    ok i already copied and pasted it to a word document. and ive used the equations for more than one of the other problems i have!

  17. tcarroll010
    • one year ago
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    You very nice to work with because you really want to learn (all students should be that way) and you are a nice person.

  18. kdarnell08
    • one year ago
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    thank you! i appreciate that. maybe its because they are mostly in high school. im in nursing school and am relearning everything and harly remember it all. i personallt DO NOT want to have to repay for this class. hs was 5 years ago so its a little more than rocky.

  19. kdarnell08
    • one year ago
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    and its an online class. which is way harder than on campus

  20. tcarroll010
    • one year ago
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    This is good what you just said. You are approaching this from a perspective that is more mature than high school. And the world needs good nurses. My sister is a nurse. She was also a math whiz, so she breezed through math. But just get through math since you already have a higher goal. And good luck in both math but especially the nursing!

  21. kdarnell08
    • one year ago
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    thank you!

  22. tcarroll010
    • one year ago
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    You are entirely welcome!

  23. kdarnell08
    • one year ago
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    did i mention i hate rational expressions :)

  24. tcarroll010
    • one year ago
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    lol then go with the irrational ones :-)

  25. tcarroll010
    • one year ago
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    A little math humor. There's so little material from which to get humor in math!

  26. kdarnell08
    • one year ago
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    haha. oh i am aware!

  27. tcarroll010
    • one year ago
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    I think the developers of all these math formulas are secretly laughing in their graves at all the misery they caused!

  28. tcarroll010
    • one year ago
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    I know! Maybe one day you can get a math PhD. as a patient! Payback!

  29. kdarnell08
    • one year ago
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    hahahahaha. thats funny!!! i wouldnt doubt it!! all i know is this is the only subject that i curl up in the fetal position and cry over ;)

  30. tcarroll010
    • one year ago
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    Math is tough because it is so unforgiving and as a field of study, it is so vertical. Can't go too far ahead without getting the basics.

  31. kdarnell08
    • one year ago
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    uh oh. got to another one....wanna help?

  32. tcarroll010
    • one year ago
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    vertical as in concepts building upon one another. Sure, I've got time for one more. Then I curl up and cry.

  33. kdarnell08
    • one year ago
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    \[\frac{ x ^{2}-25 }{ x+5 }\]

  34. tcarroll010
    • one year ago
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    Oh, you'll like this one because it's easier than the other one.

  35. kdarnell08
    • one year ago
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    oh god i hope so lol

  36. kdarnell08
    • one year ago
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    dont you get rid of the division and turn it to multipication

  37. tcarroll010
    • one year ago
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    Sort of. I'm going to factor the numerator:\[\frac{ (x + 5) \times (x - 5) }{ (x + 5) }\]Now, the division concept comes into play insofar as the x + 5 factor cancels out of the numerator and the denominator and you are left with: x - 5 as your answer.

  38. kdarnell08
    • one year ago
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    that i comletely understand!

  39. tcarroll010
    • one year ago
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    Either the website or my computer just went goofy.

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