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Math Help - Exponents ...

  1. #1
    Newbie
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    Jan 2008
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    Exponents ...

    Hello,

    I'm just learning about exponents and having a trouble totally understanding them. My parents signed up and paid a year's subscription for a website that allows me to download tests in math with an answer key because it is a subject that neither of them can help me with. Being bad at math runs in the family . Anyway, I have downloaded some tests on adding and subtracting exponents and it is helping me understand a bit more. But I am confused about some of the questions I have got wrong the answers on the answer key do not make sense to me. I am wondering if there are perhaps the odd mistake on the answer keys. Could someone help me with the following ...

    The question:

    1. (c^5 + c^2) x (c^6 x c^8)

    My answer: c^7 x c^14
    = c^21

    Key answer: c^19 + c^16

    My answer is possibly wrong but I have not got a clue about the key answer.

    2. 7^7 + 7^7 x 7^7 x 7^7

    My answer: 7^14 x 7^10
    = 7^24

    Key answer: 7^7 + 7^17

    My answer is possibly wrong but I have not got a clue about the key answer.

    A general question. In addition if the base is the same do you add the exponents and leave the base as is or do you figure out the exponents meaning the answer to this question should be...

    eg. 6^3 + 6^2 + 6^2
    = 6^9

    or

    6 x 6 x 6 + 6 x 6 + 6 x 6
    =216 + 36 + 36
    =288

    Thank you.

    walrus
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  2. #2
    GAMMA Mathematics
    colby2152's Avatar
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    Alexandria, VA
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    Quote Originally Posted by walrus View Post
    Hello,

    I'm just learning about exponents and having a trouble totally understanding them. My parents signed up and paid a year's subscription for a website that allows me to download tests in math with an answer key because it is a subject that neither of them can help me with.
    Out of curiosity, what website was it?

    Quote Originally Posted by walrus View Post
    1. (c^5 + c^2) x (c^6 x c^8)

    My answer: c^7 x c^14
    = c^21

    Key answer: c^19 + c^16
    There is an addition term in the first parenthesis, so we should expect at least two terms in our final answer.

    (c^5 + c^2) (c^6 * c^8) = (c^5 + c^2) (c^{14}) \Rightarrow c^5c^{14}+c^2c^{14} = c^{19}+c^{16}

    Your problem was that you treated that first addition sign as a multiplication sign and added all of the exponents together.

    Quote Originally Posted by walrus View Post
    2. 7^7 + 7^7 x 7^7 x 7^7

    My answer: 7^14 x 7^10
    = 7^24

    Key answer: 7^7 + 7^17

    My answer is possibly wrong but I have not got a clue about the key answer.
    7^7 + 7^7 * 7^7 * 7^7 = 7^7 + 7^{21}

    Either the answer key or your representation of the problem is wrong.

    Quote Originally Posted by walrus View Post
    A general question. In addition if the base is the same do you add the exponents and leave the base as is or do you figure out the exponents meaning the answer to this question should be...

    eg. 6^3 + 6^2 + 6^2
    = 6^9

    or

    6 x 6 x 6 + 6 x 6 + 6 x 6
    =216 + 36 + 36
    =288
    You only add the exponents when like bases are multiplied together. When they are added, you cannot do much for simplification purposes.
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  3. #3
    Newbie
    Joined
    Jan 2008
    Posts
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    Exponents ...

    Colby2152: Thank you very much for your help I don't quite understand how you got the answers you did but I'm going to go through them thoroughly until I do.

    The website is edHelper.com - Math, Reading Comprehension, Themes, Lesson Plans, and Worksheets It is really cool but I am finding the occasional incorrect answer.
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