Results 1 to 6 of 6

Math Help - Add subtract polynomials, Multiplying with monomials

  1. #1
    Newbie
    Joined
    Feb 2007
    Posts
    4

    Add subtract polynomials, Multiplying with monomials

    Im having trouble with three problems.

    1.Simplify (-5b*3x)*4.

    I got 626b*7x*4

    2. Simplify -2x(x-3) + x(5-x).


    3. Multiply: a*2b - 3ab*2 +5b*3

    -2ab
    _________________

    I got -2a*3b*2 + 6a*2b*3 - 10ab*4
    Follow Math Help Forum on Facebook and Google+

  2. #2
    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 fyisvd View Post
    Im having trouble with three problems.

    1.Simplify (-5b*3x)*4.

    I got 626b*7x*4

    2. Simplify -2x(x-3) + x(5-x).


    3. Multiply: a*2b - 3ab*2 +5b*3

    -2ab
    _________________

    I got -2a*3b*2 + 6a*2b*3 - 10ab*4
    1. How did you get that answer for 1? are you sure you typed the problem correctly? becuase * means multiply, you would end up with

    -60xb

    2. Simplify -2x(x-3) + x(5-x)

    First we expand the brackets for -2x(x-3) we multiply everything in the brackets by -2x to get -2x^2 + 6x, for the x(5-x) we multiply everything in the brackets by x to get 5x - x^2, so we end up with something like this

    -2x(x-3) + x(5-x) = -2x^2 + 6x + 5x - x^2 = -3x^2 + 11x

    3. I assume your question is: Multiply: a*2b - 3ab*2 +5b*3
    by -2ab. Okay, can you clarify for me. do you use the * to mean a power? for example when you type a*2, do you mean a squared?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2007
    Posts
    4
    Yes i meant a power when i used *. Im sorry i should have carified that. Do you use something different on this site. Im just used to using*.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    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 fyisvd View Post
    Yes i meant a power when i used *. Im sorry i should have carified that. Do you use something different on this site. Im just used to using*.
    Yes, we use ^. so everywhere i see * i should just read ^, okay got it
    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 fyisvd View Post
    Im having trouble with three problems.

    1.Simplify (-5b^3*x)^4.

    I got 626b^7x^4

    2. Simplify -2x(x-3) + x(5-x).


    3. Multiply: a^2*b - 3ab^2 +5b^3 by -2ab
    _________________

    I got -2a^3*b^2 + 6a^2*b^3 - 10ab^4

    Note: * means "multiply", ^ means "to the power"

    1.Simplify (-5b^3*x)^4

    Okay, first let us recall some rules.

    (ab)^c = a^c * b^c or similarly (a^x*b^y)^c = a^(x*c) * b^(y*c)

    okay, so we have (-5)^4 * (b^3)^4 * x^4 = 625b^12*x^4 .....we multiply the powers in this case, not add, so we get b^12 not b^7 as you had.

    When do we add powers? We do that when multiplying simialr bases, that is,
    b^a * b^c = b^(a + c)

    2. Simplify -2x(x-3) + x(5-x), i believe this question was okay to begin with, no confusion here, check my one of my previous posts for the answer.


    3. Multiply: a^2*b - 3ab^2 +5b^3 by -2ab

    so we have -2ab(a^2*b - 3ab^2 +5b^3) we multiply each term by -2ab to obtain:

    -2 * a*a^2 * b*b -2(-3)*a*a * b*b^2 + (-2)(5)*a*b*b^3
    = -2a^3*b^2 + 6a^2*b^3 - 10ab^4
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Feb 2007
    Posts
    4
    Thank you. It makes sense to me now.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Multiplying Polynomials
    Posted in the Algebra Forum
    Replies: 2
    Last Post: September 17th 2011, 10:19 AM
  2. Multiplying and Dividing Polynomials?
    Posted in the Algebra Forum
    Replies: 3
    Last Post: December 17th 2009, 12:12 PM
  3. multiplying polynomials.
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 21st 2009, 10:50 PM
  4. Multiplying Monomials
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: February 26th 2008, 06:22 PM
  5. [SOLVED] Multiplying Polynomials?
    Posted in the Algebra Forum
    Replies: 10
    Last Post: February 5th 2008, 03:41 PM

Search Tags


/mathhelpforum @mathhelpforum