# Practice GMAT Problem Solving Question

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If x is a positive integer and z is a non-negative integer such that (2,066)

^{z}is a divisor of 3,176,793, what is the value of z^{x}- x^{z}?Correct Answer:

**B**- An odd integer (e.g., 3,176,793) is not divisible by an even integer. For example, 3 is not divisible by 2 nor is 15 divisible by 2.

(3,176,793/even integer) --> non integer - The only way (2,066)
^{z}can possibly be a divisor of 3,176,793 is if (2,066)^{z}is an odd number. However, if z is any positive integer, (2,066)^{z}will be an even number. (More specifically, it will have a units digit of 6). As a result, (2,066)^{z}will not be a factor of 3,176,793 if z is a positive integer. - Since the question explicitly says that (2,066)
^{z}is a factor of 3,176,793, you know that, somehow, (2,066)^{z}must be an odd number. - Remember that any number raised to the power of 0 will be 1.

(any real number)^{0}= 1 - The key to this problem is realizing that if z = 0, which is allowed because the question stem said z "is a non-negative number," (2,066)
^{z}will equal 1. Since the only way z can be a factor 3,176,793 is if z = 0, you know that z = 0.

(3,176,793/(2,066)^{0}) is the only way 2,066^{z}is a factor of 3,176,793 - You can now rewrite the question as follows:

0^{(any positive integer)}– (any positive integer)^{0}

z^{x}– x^{z}= 0^{x}– x^{0}= 0^{(pos int)}– (pos int)^{0} - Since 0 raised to any positive integer equals 0 and any positive integer raised to 0 is 1, the question boils down to: 0 – 1 = -1.

0^{(pos int)}– (pos int)^{0}= 0 – 1 = -1

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