Answers

2015-05-12T02:06:08+05:30
In view of using the identity a^2-b^2=(a+b)(a-b), split the middle term as 2x^2-9x^2 :

x^4\underbrace{-7x^2}+1

=x^4\underbrace{+2x^2-9x^2}+1

=(x^4+2x^2+1)-(9x^2)

=(x^2+1)^2-(3x)^2~~~\because~a^2+2ab+b^2=(a+b)^2

=(x^2+1+3x)(x^2+1-3x)

=(x^2+3x+1)(x^2-3x+1)
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