math question


Last Updated:

  1. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598
    square root of (2x-5) + square root of (x+1)=3

    Any one??

    all the math websites blow ass and its 2am, class early tomorrow morning
     

    Advertisement
  2. eyebeam

    eyebeam Well-Known Member

    Joined:
    Nov 6, 2009
    Messages:
    5,418
    Likes Received:
    3,091
    Damn, I wish you had asked this earlier - Eyebette teaches this kind of stuff daily as part of her job, but alas, she's gone to bed. Sorry man and good luck!
     
  3. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598
    its cool player, thanks though

    damn me and my procrastinating!!


    teach lets us take tests home and its due tomorrow morning, waited till now to finish up last 2 questions, o well
     
  4. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598
    2nd question

    x^5 - 9x^3 + 8x^2 - 72 = 0
     
  5. VegasOnAcid

    VegasOnAcid Well-Known Member

    Joined:
    May 29, 2010
    Messages:
    1,758
    Likes Received:
    160
    I am sure you can find a website to just plug the equations into?

    On another note, I was always good at math.. but looking at that I have no clue what to do, or what your even looking for.. I remember doing something like it.. but ya. dunno why they teach that... You only use that type of math in a select fields.. no real practical use.
     
  6. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598
    i'm with ya there player.... all the websites i tried are bunk. thought i'd throw a hail mary up before i crashed, its cool
     
  7. darklide

    darklide Well-Known Member

    Joined:
    Aug 19, 2010
    Messages:
    595
    Likes Received:
    21
    I'll try, to get rid of the square root you must square the square root and get.

    2x - 5 + x +1 =9

    Add the -5 and the +1 and get -4. Then add the 2x and the x .

    3x -4 = 9

    Add the -4 to both sides.

    3x = 13

    Divide both sides by 3 and get X = 13/3

    * Doesn't seem right ,but not sure if I understand the question, sorry.
     
    NightAngel79 likes this.
  8. darklide

    darklide Well-Known Member

    Joined:
    Aug 19, 2010
    Messages:
    595
    Likes Received:
    21
    This question really doesn't make sense as they are all to the power of something different. So they cant be added together.

    So if this makes sense to do.

    Although the variables are the same (x), the powers are not the same (1, 2,and 5). You can't simplify these terms because only the variables are the same, and both the variables and the powers need to be the sam
     
  9. dunn2010

    dunn2010 Active Member

    Joined:
    Sep 10, 2010
    Messages:
    40
    Likes Received:
    6
    that seems right to me, as for your second question, that surely can't be a simplify question?
     
  10. MJM128

    MJM128 Well-Known Member

    Joined:
    Apr 1, 2010
    Messages:
    256
    Likes Received:
    31
    Lets see of how much help I can be as it's also 2am for me.

    First off darklide that's a good attempt but your starting set up was wrong. You have to square BOTH ENTIRE sides. So, the easiest method is to put one square root on one side, and the other on the other side. (makes for simpler math also known as a better solution.)


    sqrt(2x-5) + sqrt(x+1)=3


    1. Move one square root to the other side.

    sqrt(2x-5)=3-sqrt(x+1)

    2. Square both sides. The ENTIRE sides.

    (sqrt(2x-5))^2=(3-sqrt(x+1))^2
    (
    3. Simplify it The square of a binomial. Perfect square trinomials - A complete course in algebra Check this link if you have problems with taking the square of a binomial. It takes the form of (a-b)^2=(a^2-2ab+b^2) which is what you get when you times out (a-b)(a-b)

    2x-5=9-6sqrt(x+1)+(x+1)

    9. Move over terms.
    x-15=-6sqrt(x+1)

    10. Square both sides again to remove sqrt.

    (x-15)^2=(-6sqrt(x+1)^2

    11. Simplify using (a-b)^2 formula again for the left side this time.

    x^2-30x+225=36(x+1)

    12. Move everything to one side making the equation = to 0 and now it's a quadratic equation which you can solve either by completing the square, factoring, or by the quadratic formula.

    x^2-66x+189=0

    13. Since this is able to factor, I will use that method. And the factor form is

    (x-63)(x-3)=0

    14. Solve for x
    X=63, x=3

    15. NOW IS THE MOST IMPORTANT PART. YOu have to check each value of x to make sure that when plugged back into the original equation to make sure we don't have a negative number in the root, and that the statement is equal to 3.

    16. The answer is x=3 since 63 gives us 19 as the answer, while when you plug in 3 for the value of x you get 3 the equation is true.
     
    NightAngel79 likes this.
  11. MJM128

    MJM128 Well-Known Member

    Joined:
    Apr 1, 2010
    Messages:
    256
    Likes Received:
    31
    1. I believe this problem is solved by factoring by grouping.
    So try grouping it by what you can factor out.

    x^5-9x^3+8x^2-72=0


    2. Factor what you can on each side. What I put in parenthesis is what I see can be factored.

    (x^5-9x^3)+(8x^2-72)=0

    3. For the left pair you can take out x^3 and for the right you can take out 8.

    x^3(x^2-9)+8(x^2-9)=0

    4. Notice how what we're left with is the same, that's a GOOD sign, that what we have is right.

    So what you do with that is bring what is the same in the parenthesis and that's one factor, and then what's left on the outside as another factor.

    So: (x^3+8)(x^2-9)=0


    5. Set each factor as equal to 0 and solve.


    6a Solving for the left factor gives.

    (x^3+8)=0

    Factor it more using the formula (a^3+b^3)=(a+b)(a^2-ab+b^2)


    So; (x+2)(x^2-2x+4)=0


    For the real number part (x+2)=0 so


    x=-2


    And then solve that quadratic equation using either completing the square or the quadratic formula which will give you

    x = 1-i sqrt(3) and x = 1+i sqrt(3) as the complex answer.

    Back to the other part of the factor from earlier: (x^2-9)=0


    1. Move the number to the right side and square root, or factor it. Either method.

    x^2=9
    x=+or-3
    so x=3 x=-3

    So all the answers to that problem are:

    x=3
    x=-3 x=-2
    x=1-isqrt(3)
    x=1+isqrt(3)
     
    NightAngel79 likes this.
  12. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598
    That was where i was going with that also. and it worked for me. until the end... looks good to me!! thanks for the help player!!
     
  13. MJM128

    MJM128 Well-Known Member

    Joined:
    Apr 1, 2010
    Messages:
    256
    Likes Received:
    31
    You're welcome, just maybe next time procrastinate a little less so you can get an answer sooner? :p

    Also if you don't have a dedicated program for solving equations like this you can try using Wolfram|Alpha—Computational Knowledge Engine It does a pretty good job, that and a combo of google works wonders for checking problems. :D
     
    NightAngel79 likes this.
  14. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598
    Yea procrastination is a disease that I suffer from. Not sure what all sites I tried last night but have up on them late last night. Didn't even think to just Google the actual equations.
    /facepalm.....
    Good looking out though, that was just what I needed player
     
  15. bearsfan85

    bearsfan85 Well-Known Member Developer

    Joined:
    Feb 23, 2010
    Messages:
    459
    Likes Received:
    97
    wolframalpha.com
     
    NightAngel79 likes this.
  16. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598


    Thanks for everyone's help. Wolframalpha is a great site but it doesn't show the work, i.e. how they got to the answer... still... didn't know about that site at all and will use it in the future if/when i get stuck.

    Again, thanks guys
     
  17. Roxors

    Roxors Well-Known Member

    Joined:
    Jul 8, 2010
    Messages:
    696
    Likes Received:
    121
    Bad Mayer!!! im telling the teacher!! :p
     
  18. Rota

    Rota Well-Known Member

    Joined:
    Feb 14, 2010
    Messages:
    454
    Likes Received:
    68
    Amazing website when you're stuck on a math problem.

    Also, I wish math was still this easy. Differential Equations and Multivariable Calculus FTL. :(
     
  19. NightAngel79

    NightAngel79 Bounty Hunter Administrator Moderator This Topic's Starter

    Joined:
    May 11, 2010
    Messages:
    22,332
    Likes Received:
    7,598
    What? its a take home test, plus my man ^^ up there worked it out so well i was able to see what he did, work it out myself and remember wtf i was supposed to do:rolleyes::rolleyes:
    Damn!! I know who i'm pm'ing next time:D;)
     
  20. Roxors

    Roxors Well-Known Member

    Joined:
    Jul 8, 2010
    Messages:
    696
    Likes Received:
    121
    Well then.... i fail lol



    i didn't even know what that meant
     
  21. death2all110

    death2all110 VIP Member VIP Member

    Joined:
    Jun 25, 2010
    Messages:
    1,995
    Likes Received:
    1,208
    Its algebra. simple. Mathematics my dear Roxors
     

Share This Page

Loading...