# `(1-x)(1+x^2)(1+x)(1+x^2)` equals:a.1-x^6b.1+x^6c.1-x^8d.1+x^8e. None of the above

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### 2 Answers

None of the original answer choices is correct, so I added a choice e. We can rearrange and then use the difference of squares formula twice.

`(1-x)(1+x)(1+x^2)(1+x^2)=(1-x^2)(1+x^2)(1+x^2)`

`=(1-x^4)(1+x^2)=1+x^2-x^4-x^6.`

This is the second multiple choice question you've posted recently where all the answer choices are wrong. If you're getting them from a book, I suggest finding a new book :)

**Sources:**

based on the calculations on my paper it is e