Pre-Algebra

Can I have some help please.

4. (3x+4)(x - 2)
A. 3x^2-2x-8
B. x-8
C. 3x-2x-8
D. 3x^2+2x+8

5. (2y-1)(4y-3)
A. -2y+3
B. 8y^2-10y-3
C. 8y^2-10y+3
D. 8y^2-2y+3

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  1. (3x+4)(x - 2)
    If you expand this out...
    The 3x has to be multiplied by both elements in the second bracket
    The 4 must also be multiplied by both elements in the second bracket
    (3x)(x) -2(3x) +4(x) +4(-2)
    = 3x^2 -6x +4x - 8
    Then you have to collect like terms (the x's)
    = 3x^2 - 2x - 8
    You really have to watch the signs :) Just hold onto the sign in front of the parts and pieces you are working with...
    YOUR TURN...

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  2. ....and by the way, Google distributive property of multiplication
    for example:
    http://www.math-worksheet.org/multiplying

    the way I think of it is
    (a+b+c)(d+e+f)
    =
    a(d+e+f) +b(d+e+f) +c(d+e+f)
    = ad+ae+af+bd+ ....... get it :)

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  3. yes I get it Thank you :)

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