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Algebra and Finding a fomula

  1. Dec 1, 2004 #1
    I know it's easy to all you people, but my first question is, is this right:

    Difference between ( X) x (X+21) and (X+1) x (X+20)=20
    =(x²+x+20x+20)-(x²+21x)
    =(x²+21x+20)-(x²+21x)
    =(21x+20)-21x
    =20

    I think it is, that's one point

    Point 2
    I just can't find an expression which connects N(or Size) with Difference

    N Size Difference
    1 2x2 40
    2 3x3 160
    3 4x4 240
    4 5x5 640




    Thanks In Advance
     
  2. jcsd
  3. Dec 1, 2004 #2
    I am not sure what you are asking about with the N difference... what exactly are you solving for?
     
  4. Dec 1, 2004 #3

    Diane_

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    Homework Helper

    I know it's easy to all you people, but my first question is, is this right:

    Difference between ( X) x (X+21) and (X+1) x (X+20)=20
    =(x²+x+20x+20)-(x²+21x)
    =(x²+21x+20)-(x²+21x)
    =(21x+20)-21x
    =20


    Well, the first one resolves to x^2 + 21x. It's an expression, not an equation, so it can't be "solved" per se - just simplified or rewritten.

    The second is an equation - trite though it may sound, it has an "equals" sign. The left side of the second is clearly not equivalent to the first. Think of it like this: let x have a value, say 10. The first, then, would be the same as

    (x)(x + 21) = 10 * 31 = 310

    The second would be

    (x + 1)(x + 20) = 11 * 30 = 330

    Clearly not the same.

    Does that answer your question? If not, could you be a little more specific? (Gee, I'm saying that a lot tonight...)
     
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