Q5 of 53 Page 166

Factorise the following:

x4 + 5x2 + 9.

⇒ x4 + 5x2 + 9


⇒ x4 + 6x2 + 9 – x2


⇒ (x2)2 + 2 × 3 × x2 + 32 – x2


⇒ (x2 + 3)2 – x2


⇒ (x2 + 3 + x) (x2 + 3 – x)
Since,


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