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Math Help - Answer Verification

  1. #1
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    Answer Verification

    I am trying to bring up my math grade and was hoping someone could help me out simply by verifying my homework answers are incorrect (and indicating which aren't). I imagine it would only take a few minutes for those who are familiar with these types of problems (binomial multiplication).

    Multiply using FOIL method:

    Problems
    Answers

    1: (x + 9)(x + 2)
    1: x^2 + 11x + 18
    2: (4x - 11)(x + 6)
    2: 4x^2 + 13x - 66
    3: (3x - 13)(x - 2)
    3: 3x^2 - 19x + 26
    4: (y^2 + 7)(2y^2 - 9)
    4: 2y^4 + 5y^2 - 63
    5: (x - 3/10)(x + 1/5)
    5: x^2 - 1/10x - 3/15
    6: (4 - 6a)(2 - 3a)
    6: 8 - 24a - 18a^2
    7: (x + 8y)(3x - 4y)
    7: 3x^2 + 20xy - 32y^2

    Multiply

    8: (x + 12)^2
    8: x^2 + 144
    9: (10a - 3)^2
    9: 10a^2 - 9
    10: (y - 3/5)^2
    10: y^2 - 9/25
    11: (2y - 13)^2
    11: 2y^2 - 169
    12: (x - 11)(x + 11)
    12: x^2 + 121
    13: (4x - 10)(4x + 10)
    13: 4x^4 - 100
    14: (3y^2 - 5)(3y^2 + 5)
    14: 3y^4 - 25
    15: (3x - 1/6)(3x + 1/6)
    15: 9x - 1/36
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  2. #2
    MHF Contributor
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    In the first group (1--7), check 5 and 6. In the second, group, unfortunately, all are wrong. For example, (x + 12)^2 = x^2 + 24x + 144.

    You can check such calculations online at WolframAlpha. Just type (x + 12)^2, press Enter, and look for Alternate forms. But remember that with great power come great responsibility. I mean that if you are ever going to need to solve these problems by hand, you most certainly must train hard in doing this by hand.
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  3. #3
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    Quote Originally Posted by emakarov View Post
    In the first group (1--7), check 5 and 6. In the second, group, unfortunately, all are wrong. For example, (x + 12)^2 = x^2 + 24x + 144.

    You can check such calculations online at WolframAlpha. Just type (x + 12)^2, press Enter, and look for Alternate forms. But remember that with great power come great responsibility. I mean that if you are ever going to need to solve these problems by hand, you most certainly must train hard in doing this by hand.

    Awesome! thanks for your help and the link. I mistyped the answer for number 6, BTW. It was supposed to say +18a^2 instead of -18a^2. I also saw where I messed up with #5. With the rest, the change in directions threw me off. I assumed I was supposed to do them differently (ie a non-FOIL method) since instructions were resupplied with the FOIL-part omitted.

    Anyway, that link will help me a lot in the future with checking my work. You're right about becoming too dependent on it. I will only use it to verify what I have learned and where I need to focus my efforts/studies because I really need to learn to do this stuff better.

    Once again, thanks a lot for your help
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