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# If x is odd, all EXCEPT which one of the following must be odd?

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If x is odd, all EXCEPT which one of the following must be odd?  [#permalink]

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31 Aug 2018, 00:01
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69% (01:15) correct 31% (00:58) wrong based on 62 sessions

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If x is odd, all EXCEPT which one of the following must be odd?

(A) $$x^2 + 4x + 6$$
(B) $$x^3 + 5x + 3$$
(C) $$x^4 + 6x + 7$$
(D) $$x^5 + 7x + 1$$
(E) $$x^6 + 8x + 4$$

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Re: If x is odd, all EXCEPT which one of the following must be odd?  [#permalink]

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31 Aug 2018, 00:15
Since x is odd.

Lets take x = 1.

Only option C is even. Rest all are odd.

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If x is odd, all EXCEPT which one of the following must be odd?  [#permalink]

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31 Aug 2018, 00:48
Bunuel wrote:
If x is odd, all EXCEPT which one of the following must be odd?

(A) $$x^2 + 4x + 6$$
(B) $$x^3 + 5x + 3$$
(C) $$x^4 + 6x + 7$$
(D) $$x^5 + 7x + 1$$
(E) $$x^6 + 8x + 4$$

To find:-All EXCEPT which one of the following must be odd?
Implies that 4 incorrect answer options yield ODD output & one correct answer option yields EVEN output.

Three terms are there in each of the expressions in the answer options.

Note:-
1) An odd number in exponent form($$Odd^{integer}$$) is always odd.
2) Multiplication of odd numbers always yield odd number.
3) Multiplication of odd numbers by even numbers always yield even number.
A. O+E+E=O
B. O+O+O=O
$$C. O+E+O=E$$
D. O+O+O=O
E. O+E+E=O

Ans. (C)
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Re: If x is odd, all EXCEPT which one of the following must be odd?  [#permalink]

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31 Aug 2018, 01:08
Put x=1 in the answer choice. All the options give odd result except C.
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If x is odd, all EXCEPT which one of the following must be odd?  [#permalink]

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18 Sep 2018, 06:29
Bunuel wrote:
If x is odd, all EXCEPT which one of the following must be odd?

(A) $$x^2 + 4x + 6$$
(B) $$x^3 + 5x + 3$$
(C) $$x^4 + 6x + 7$$
(D) $$x^5 + 7x + 1$$
(E) $$x^6 + 8x + 4$$

Another way to look at this problem is to regognize that x^n will always be odd in all options. In A and E booth other terms are even, so A and E booth result in an odd number. In B and D booth other terms are odd, so B and D will booth result in an odd number.

Only option C has an even and odd term, and will therefore result in an even number. Hence C is the answer.
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Re: If x is odd, all EXCEPT which one of the following must be odd?  [#permalink]

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19 Sep 2018, 18:05
Bunuel wrote:
If x is odd, all EXCEPT which one of the following must be odd?

(A) $$x^2 + 4x + 6$$
(B) $$x^3 + 5x + 3$$
(C) $$x^4 + 6x + 7$$
(D) $$x^5 + 7x + 1$$
(E) $$x^6 + 8x + 4$$

Recall that even x odd = even and odd x odd = odd. Let’s analyze each choice.

A) x^2 + 4x + 6

odd + even + even = odd

B) x^3 + 5x + 3

odd + odd + odd = odd

C) x^4 + 6x + 7

odd + even + odd = even

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Re: If x is odd, all EXCEPT which one of the following must be odd? &nbs [#permalink] 19 Sep 2018, 18:05
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# If x is odd, all EXCEPT which one of the following must be odd?

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