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Math Help - Expanding expressions

  1. #1
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    Expanding expressions

    Im not too sure how to expand these two expressions

    1/ (x+2y)(x-2y)2

    2/ (1-x)(1+x+x2+x3)


    The small numbers r squared and cubed.. not sure how to use it here

    Would be good if you can put steps also so i can understand where it comes from..

    Thanks
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  2. #2
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    Hi fvaras89

    Example
    To type square : x^2
    To type cube : x^3

    or you can learn it here : http://www.mathhelpforum.com/math-he...-tutorial.html

    These are hints to help you solve those problems:
    1. (x+1)^2 = (x+1) * (x+1) = x^2 + x + x + 1 = x^2 + 2x + 1

    2. (x+1)\cdot(x^2+3x+5) = x\cdot x^2 + x\cdot 3x + x\cdot 5 + 1\cdot x^2 + 1\cdot 3x + 1\cdot 5 = x^3 + 4x^2 + 8x + 5
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  3. #3
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    Thanks, but im really still not sure what to do.. any more hints?
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  4. #4
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    Hi fvaras89

    Can you expand (x+5)^2 ?
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  5. #5
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    Is that how you would expand it?

    x^2 + 25x + 25
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  6. #6
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    Hi fvaras89

    Almost right. How can you get 25x ?
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  7. #7
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    oh woops hahah..

    so would it be x^2 + 25?
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  8. #8
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    Hi fvaras89

    Still no.

    (x+a) \cdot (y+b) = x \cdot y + x \cdot b + a \cdot y + a \cdot b
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  9. #9
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    Do you have a text book that you are working from? I doubt your teacher would give you a task if you're not clear.

    I'll use songoku's question:

    (x+5)^2

    since the power is 2 it's multiplying itself.

    for example 2^2

    =  2 * 2

    now we do the same for this..

     (x+5)(x+5)

    now we multiply the first number/letter of the first bracket by the first number/letter of the second bracket

     x * x = x^2

    now we multiply the first letter of the first bracket by the second number/ letter

     x * 5 = 5x

    now we multiply the second letter/number by the first number of the second bracket

     5 * x = 5x

    now the last step... yep that's right, the second number/letter of the first bracket by the second number/letter of the second bracket.

     5 * 5 = 25

    do you get the pattern?

    Now put them together

     x^2 + 5x + 5x + 25

    simplify..

     x^2 + 10x + 25

    now that you've learnt how to do it properly now I tell you the shortcut

    when you have 2 brackets multiplying each other and they are IDENTICAL. They have to be identical.

    The formula:

     a^2 + 2ab + b^2 can be used.. for example:

     (x+5)^2

    x will be "a" and 5 will be "b"

    now just substitute:

     a^2 + 2ab + b^2

     x^2 + 2*x*5 + 5^2

     x^2 + 10x + 25

    Was that the same answer as before? it sure was.

    Do you understand better now?
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  10. #10
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    help

    i dont understand 6(x+4)
    7(3x-9)
    x(x+7)
    help please
    as soon as thanks
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  11. #11
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    WHAT are you asked to do?
    Please post problem IN FULL.
    I suggest you start your own thread.
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  12. #12
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    Sorry i am new to this...
    i am asked to expand these alebraic expressions
    5(x+5)
    9(8x-9)
    x(x+8)
    and i really dont understand them so please could you help
    thanks Natalie B
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  13. #13
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    Quote Originally Posted by NatalieB View Post
    i am asked to expand these alebraic expressions
    5(x+5)
    9(8x-9)
    x(x+8)
    Means multiply what's inside brackets by what's outside.
    Take 5(x+5)
    5 times x = 5x
    5 times 5 = 25
    So answer is 5x + 25

    Let's see you do the other 2: GO Natalie GO
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  14. #14
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    These are hints to help you solve those problems:
    1.

    2.
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  15. #15
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    Okayy so is this correct ...?
    9(8x-9)
    9 times 8x=72x
    9 times 9 = 81
    so its 72x-81

    P.S
    how do you add the quote in at the top of the page ???
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