Algebra

Hiya. I have 7 expressions that I have been asked to simplify. I worked all of them out, and if you could, I'd like you to check my work for me.

Here they are:

1. (x^2 + 3x - 9) + (-4x^2 + 2x - 3)

My answer: -4x^4 + 5x - 12

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

My answer: 3x^2 - 30x - 10

3. (r + 3)^2

My answer: r^2 + 6r + 9

4. (p^2 + 4p - 23) - (3p^2 - 23p - 23)

My answer: 3p^4 - 19p - 46

5. (5z - 2)(5z + 2)

My answer: 25z^4 - 4

6. (2m - 4)(m^2 + 2m + 4)

My answer: 2m^3

7. (3x - 2)(2x - 3)

My answer: 6x^2 - 13x + 6

I know there were quite a few there, so I really appreciate you helping me out. If I made any mistakes, please let me know what I did wrong so I can correct it. Thank you so much!

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asked by Kathy
  1. 1. (x^2 + 3x - 9) + (-4x^2 + 2x - 3)

    My answer: -4x^4 + 5x - 12
    -------------------------------
    my answer, add like terms
    x^2 - 4 x^2 = - 3 x^2 for example

    -3 x^2 + 5 x -12

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    posted by Damon
  2. 2. (x - 2)(3x + 5)

    My answer: 3x^2 - 30x - 10
    ---------------------------
    My answer, either FOIL or use distributive property
    FOIL
    3 x^2 + 5 x - 6 x -10
    = 3 x^2 - x - 10
    distributive property
    x(3x+5) -2(3x+5)
    3 x^2 + 5 x - 6 x - 10 remarkably similar

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    posted by Damon
  3. #1 should be
    -3x^2 + 5x- 12

    #2
    3x^2+ 5x - 6x - 10 = 3x^2- x - 10

    #3, good, yeahhh
    #4, -2p^2 + 27p
    #5, yeahhh
    #6 good grief!!!
    = 2m^3 + 4m^2 + 8m - 4m^2 - 8m - 16
    = 2m^3 - 16

    #7, correct

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    posted by Reiny
  4. 3. (r + 3)^2

    My answer: r^2 + 6r + 9 YES

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    posted by Damon
  5. something like 6 use that distributive property
    6. (2m - 4)(m^2 + 2m + 4)
    2m (m^2 + 2m + 4) = 2 m^3 +4 m^2 + 8 m
    -4 (m^2 + 2m + 4) = 0 m^3 -4 m^2 - 8 m -16
    -----------------------------------add
    2 m^3 -16

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    posted by Damon
  6. Thanks Damon and Reiny for your help!

    1. 👍 0
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    posted by Kathy

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