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Math Help - expand and simplify

  1. #1
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    expand and simplify

    hi this is my question:
    3x^2+4+x(x-1)
    for this i know i would do
    3x^2+4
    but after that im kinda stuck!
    would i do
    3x^2+4 2x-x = 3x^2+x+4??
    could you help please?
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  2. #2
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    x(x-1) = x \cdot x + x \cdot -1 = x^2-x

    Since multiplication is higher than addition in the order of operations you need to add x^2-x such that you get 3x^2+4+(x^2-x)
    Last edited by e^(i*pi); September 17th 2010 at 06:00 AM. Reason: Because x*-1 = -x not -1
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  3. #3
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    Quote Originally Posted by andyboy179 View Post
    hi this is my question:
    3x^2+4+x(x-1)
    for this i know i would do
    3x^2+4
    but after that im kinda stuck!
    would i do
    3x^2+4 2x-x = 3x^2+x+4??
    could you help please?
    Hi andyboy179,

    you need to know how to multiply out the terms of x(x-1)

    You do it the exact same way as 3(3-1)=3(2)=6

    3(3-1)=3(3)+3(-1)=9-3=6

    Or 5(5-1)=5(4)=20

    5(5-1)=5(5)+5(-1)=25-5=20

    You just multiply the x by both terms inside the brackets

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

    Now combine that with 3x^2+4

    Can you continue from there?
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  4. #4
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    Quote Originally Posted by Archie Meade View Post
    Hi andyboy179,

    you need to know how to multiply out the terms of x(x-1)

    You do it the exact same way as 3(3-1)=3(2)=6

    3(3-1)=3(3)+3(-1)=9-3=6

    Or 5(5-1)=5(4)=20

    5(5-1)=5(5)+5(-1)=25-5=20

    You just multiply the x by both terms inside the brackets

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

    Now combine that with 3x^2+4

    Can you continue from there?
    would the answer be 1x+4?
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  5. #5
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    Quote Originally Posted by andyboy179 View Post
    would the answer be 1x+4?
    How are you getting that?
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  6. #6
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    Quote Originally Posted by Archie Meade View Post
    How are you getting that?
    3x^2+4 x^2-x
    i took away the ^2 from both because both have them
    so iam left with 3x+4 x-x
    3x-x= 2x
    2x-x=x
    then i have 4 left over so answer is x=4?
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  7. #7
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    Quote Originally Posted by andyboy179 View Post
    3x^2+4 x^2-x
    i took away the ^2 from both because both have them
    so iam left with 3x+4 x-x
    3x-x= 2x
    2x-x=x
    then i have 4 left over so answer is x=4?
    You are working with some guidelines that don't apply here.

    3x^2+x^2-x+4

    You find how many x^2 terms you have, how many x terms you have and the remaining constant.

    3x^2+x^2=x^2(3+1)
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  8. #8
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    e^(i*pi)'s Avatar
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    The first line is wrong - it should state 3x^2+4+(x^2-x). Either that or the OP is wrong.
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  9. #9
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    so would i be 4x^+4-x?
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  10. #10
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    e^(i*pi)'s Avatar
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    Yes, it would although the convention on notation says that you use descending powers of x from left to right: 4x^2-x+4. But it's the same answer
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  11. #11
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    okay! i think i understand now! thank you very much!!!
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