Page 1 of 2 12 LastLast
Results 1 to 15 of 22

Math Help - algebra multiply

  1. #1
    Newbie
    Joined
    Sep 2008
    Posts
    16

    algebra multiply

    I am soo confused!
    My calculus teacher told me that you cant muliply, add, subtract.. etc. one number that is squared to a number that is not
    for example you cant multiply 3x^2 (4x)
    I remember her saying something about a FOIL method but I missed that part of the school year. I was in a different school that didnt teach this method.
    Can I do that or not?

    and can I add, multiply, etc a number with an x to a number without one?
    For example, would (4x)(-1+x) be 4x??
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Sep 2008
    Posts
    16
    wait.. no that answer is wrong, itd be -4+4x^2.. right?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by KeiaBlake View Post
    wait.. no that answer is wrong, itd be -4+4x^2.. right?
    nope, still wrong

    it is -4x + 4x^2
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Mar 2008
    Posts
    78
    3x^2*4x = 12x^3

    (4x)(-1+x) = -4x +4x^2

    This is just algebra.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by paulrb View Post
    This is just algebra.
    glad to hear that!

    review your algebra rules, KeiaBlake. you are going to have a HARD time with any math you do if you don't know algebra

    recall, x^a \cdot x^b = x^{a + b}

    now make sure you know the other rules
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Sep 2008
    Posts
    16
    Quote Originally Posted by Jhevon View Post
    nope, still wrong

    it is -4x + 4x^2
    where did that second x come from?..
    the problem was (4x)(-1+x)
    so u multiply 4x by -1 which gives u -4x and then 4x by x which gives u 4x^2
    so itd be -4x+4x^2... lol.. oh.. okay! I c! Ty!! :P
    Follow Math Help Forum on Facebook and Google+

  7. #7
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by KeiaBlake View Post
    where did that second x come from?..
    the problem was (4x)(-1+x)
    so u multiply 4x by -1 which gives u -4x and then 4x by x which gives u 4x^2
    so itd be -4x+4x^2... lol.. oh.. okay! I c! Ty!! :P
    haha, it's good to talk yourself through things sometimes
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Newbie
    Joined
    Sep 2008
    Posts
    16

    HELP AGAIN lol

    Thats true!!
    But now I really am stuck!
    lol

    f(g(2))
    f(x)= 2x+3
    g(x)=x^2-1

    is it: 2(x^2-1)+3 = 2x^2-2+3 = 2x^2-1 ??
    Any idea?
    Follow Math Help Forum on Facebook and Google+

  9. #9
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by KeiaBlake View Post
    Thats true!!
    But now I really am stuck!
    lol

    f(g(2))
    f(x)= 2x+3
    g(x)=x^2-1

    is it: 2(x^2-1)+3 = 2x^2-2+3 = 2x^2-1 ??
    Any idea?
    good so far! a lot of students couldn't make it to that point.

    how are you stuck now? just plug in 2 for x. you have f(g(x)) and you want f(g(2)), so just plug in 2
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Newbie
    Joined
    Sep 2008
    Posts
    16
    Oh yeah!..
    I'm so illiterate..
    Guess it would have been easier to just substitute that 2 in for g(x) then plug that answer into f(x).. I just don't think far enough ahead.. lol. Thanks again!
    I take it u teach this for a living?
    Follow Math Help Forum on Facebook and Google+

  11. #11
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by KeiaBlake View Post
    Oh yeah!..
    I'm so illiterate..
    Guess it would have been easier to just substitute that 2 in for g(x) then plug that answer into f(x).. I just don't think far enough ahead.. lol. Thanks again!
    yes, i was going to say that. but i was a bit scared to. don't ask why

    I take it u teach this for a living?
    nope. i'm a student just like yourself.
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Newbie
    Joined
    Sep 2008
    Posts
    16
    this dosent seem right..

    (x^2-x)(x^2-2)
    is it
    2x^4-2x^2-x^3+2x??
    :S
    If not dont tell me the answer! I wanna see if I can fix it if it's wrong.
    Follow Math Help Forum on Facebook and Google+

  13. #13
    Newbie
    Joined
    Sep 2008
    Posts
    16
    no wait!! lol
    is it
    x^4-2x^2-x^3+2x
    Follow Math Help Forum on Facebook and Google+

  14. #14
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by KeiaBlake View Post
    this dosent seem right..

    (x^2-x)(x^2-2)
    is it
    2x^4-2x^2-x^3+2x??
    :S
    If not dont tell me the answer! I wanna see if I can fix it if it's wrong.
    it's wrong
    Follow Math Help Forum on Facebook and Google+

  15. #15
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by KeiaBlake View Post
    no wait!! lol
    is it
    x^4-2x^2-x^3+2x
    haha, yup

    nice catch!
    Follow Math Help Forum on Facebook and Google+

Page 1 of 2 12 LastLast

Similar Math Help Forum Discussions

  1. Multiply
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 26th 2009, 03:20 AM
  2. How would I multiply this out?
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: September 23rd 2009, 07:50 PM
  3. how to multiply
    Posted in the Algebra Forum
    Replies: 7
    Last Post: August 4th 2008, 08:08 PM
  4. multiply algebra
    Posted in the Algebra Forum
    Replies: 3
    Last Post: December 5th 2007, 02:16 PM
  5. Multiply
    Posted in the Algebra Forum
    Replies: 1
    Last Post: April 15th 2007, 08:48 AM

Search Tags


/mathhelpforum @mathhelpforum