Results 1 to 6 of 6

Math Help - need help with algebra (long division)

  1. #1
    Newbie
    Joined
    Jul 2009
    Posts
    9

    Unhappy need help with algebra (long division)

    Hey i was wondering if anyone could help me?

    im doing some summer revision on algebra and i got stuck on this long division algebra question :

    (x + 11x - 30) (x-2)


    i keep getting the answer: x + 9x + 36

    the correct answer is : x + 2x + 15

    i would really appreciate if anyone could help me out with this, i know it seems like a very easy question for most people but maths is my worst subject
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    Hi

    Maybe your mistake comes from the fact that there is no x-term in x + 11x - 30
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jul 2009
    Posts
    9
    thanks for replying !!! though (x + 11x - 30) is the question, not the answer,

    im wondering how to get the answer : x + 2x + 15
    from the question (x + 11x - 30) divided by (x-2)

    as i am getting the same wrong answer from my numerous attempts to try solve it lol. i know that i have to add the missing factor ie.
    0x

    (x + 11x + 0 x - 30) yet to no avail can i get the right answer
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,706
    Thanks
    625
    Hello, cliste09!

    (x^3 + 11x - 30) \div (x-2)

    i keep getting the answer: . x^2 + 9x + 36 .
    How?
    I can guess how you got a "9" . . . but the "36"?

    . . \begin{array}{ccccccccc}&&&& x^2 &+&2x&-&15 \\ &&---&---&---&---&---&---&--- \\ x-2&|&x^3 &&&+&11x &-&30 \\ &&x^3&-&2x^2 \\ &&---&---&--- \\ &&&&2x^2&+&11x \\ &&&&2x^2&-&4x \\ &&&&---&---&--- \\ &&&&&&15x&-&30 \\ &&&&&&15x&-&30 \\ &&&&&&---&---&--- \end{array}

    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,525
    Thanks
    1384
    Quote Originally Posted by cliste09 View Post
    thanks for replying !!! though (x + 11x - 30) is the question, not the answer,

    im wondering how to get the answer : x + 2x + 15
    from the question (x + 11x - 30) divided by (x-2)

    as i am getting the same wrong answer from my numerous attempts to try solve it lol. i know that i have to add the missing factor ie.
    0x

    (x + 11x + 0 x - 30) yet to no avail can i get the right answer
    Running gag told you what the problem was: You need to write x^3+ 11x- 30 as x^3+ 0x^2+ 11x- 30 in order that you keep things lined up correctly. Notice that Soroban did not actually write " 0x^2" but he did leave a space for it. I prefer to write 0x^2 so as not to confuse myself! Soroban is clearly more adept at this than you or I.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Jul 2009
    Posts
    9
    thank you so much!!! you're a life-saver lol i was about to give up on it even though its not even an exam question , ahh i see where i went wrong!!!


    haha as for the 36 i got that when i did this:


    x + 9x -36
    --------------------
    x-2 { x + 11x + 0x - 30} step 1= x div. by x = x
    x - 2x + 0x step 2= x mul. by x-2= x
    ------------------
    9x + 0x step 3= 9x div. by x=9x
    9x - 18x step 4= 9x(x-2)=9x-18
    ------------------
    - 18x -30 step 5=cancel 9x,bring down -18x and -30
    - 18x-36 now -18x div. by x= 18

    step 6= -18(x-2)=-18x + 36 ( by mistake i
    must of just put 36 as the last term on
    top)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. big-o, but long division first
    Posted in the Discrete Math Forum
    Replies: 3
    Last Post: January 24th 2011, 12:45 PM
  2. long division
    Posted in the LaTeX Help Forum
    Replies: 4
    Last Post: June 28th 2009, 09:11 AM
  3. Long division
    Posted in the Algebra Forum
    Replies: 2
    Last Post: October 15th 2008, 11:44 AM
  4. Long Division
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: August 20th 2008, 03:55 PM
  5. long division
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: May 25th 2008, 11:33 AM

Search Tags


/mathhelpforum @mathhelpforum