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# If x -1, then (1 - x^16)/((1 + x)(1 + x^2)(1 + x^4)(1 + x^8)) is

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Re: If x -1, then (1 - x^16)/((1 + x)(1 + x^2)(1 + x^4)(1 + x^8)) is [#permalink]
NoHalfMeasures wrote:
If $$x\neq{-1}$$ , $$\frac{1- x^{16}}{{(1+x)*(1+x^2)*(1+x^4)*(1+x^8)}$$ is equivalent to

A. -1
B. 1
C. x
D. 1-x
E. x-1

how to pick number in this question? Bunuel
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Re: If x -1, then (1 - x^16)/((1 + x)(1 + x^2)(1 + x^4)(1 + x^8)) is [#permalink]
NoHalfMeasures wrote:
If $$x\neq{-1}$$ , $$\frac{1- x^{16}}{(1+x)*(1+x^2)*(1+x^4)*(1+x^8)}$$ is equivalent to

A. -1
B. 1
C. x
D. 1-x
E. x-1

A question in which basic formula works a^2 - b^2 = (a-b) (a+b)

Now you can expand the numerator as

1-x^16 = (1-x) (1+x) (1+x^2) (1+x^4) (1 + x^8)

Which will result in Answer D
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If x -1, then (1 - x^16)/((1 + x)(1 + x^2)(1 + x^4)(1 + x^8)) is [#permalink]