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Posted by on Sunday, August 16, 2009 at 4:29pm.

Simplify each of the following, if possible. Write your answers in exponential form, a^b

3^4*3^7*3^6

2^80+3*2^80

  • math? - , Sunday, August 16, 2009 at 4:40pm

    There are two different cases here.
    3^4*3^7*3^6 is a pure multiplicative expression, so the rules of priority and rules of exponents are applicable.
    1. exponentiation has priority over multiplication
    2. multiplication of two numbers to the same base a raised to exponents x and y yields a result of ax+y.
    So
    3^4*3^7*3^6
    = (34)*(37)*(36)
    = 34+7+6
    =317

    The second expression, 2^80+3*2^80, has two terms with a common factor 280. So the simplification consists in factorization of the expression, namely
    2^80+3*2^80
    = 1*280 + 3*280
    = (1+3)280
    = 4*280

  • math? - , Sunday, August 16, 2009 at 4:45pm

    In the second problem why do I put a 1 before 2^80?

  • math? - , Sunday, August 16, 2009 at 4:58pm

    you don't have to, but on the second step it makes factorization more apparent.

  • math? - , Sunday, August 16, 2009 at 5:04pm

    thats why the answer not 3^2^280 I am not understanding the answer

  • math? - , Sunday, August 16, 2009 at 5:06pm

    thats why the answer not 3^2^280 I am not understanding the answer


    you don't multiply 3*2=6^80

  • math? - , Sunday, August 16, 2009 at 5:39pm

    The rules of priority of operations requires us to do exponents first, so
    3*2^80 is the same as 3*(2^80). That is to say, we do the exponentiation of 2 to the power of 80 before multiplication.

    If we multiply before exponentiation, we are not following the rules of priority of operations.

    Then come the rules of exponentiation, some of the basic ones are :

    a0 = 1 for any value of a≠0
    a1 = a
    a2 = a*a
    a3 = a*a*a, etc.
    a-1 = 1/a
    a-2 = 1/(a*a)
    a-3 = 1/(a*a*a), etc.

    ax * ay = ax+y
    This rule can be applied only if the two bases (a) are the same.

    This also means that we cannot simplify ax*by for general values of a and b.

    Since the expression
    3*280
    =31 * 280
    has 3 and 2 as bases for the exponents, we cannot simplify the expression by the rules of exponents.

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