Why is x^4 - 16 when factored not just (x^2 + 4) (x^2 - 4)?
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Answer:
[tex] (x - 2)(x + 2)( {x}^{2} + 4)[/tex]
Step-by-step explanation:
[tex] {x}^{4} - 16 \\ = ({x}^{2})^{2} - ({2}^{2})^{2} \\ = ( {x}^{2} - {2}^{2} )( {x}^{2} + {2}^{2} ) \\ = (x - 2)(x + 2)( {x}^{2} + 4)[/tex]
Because [tex] (x^2 - 4) = (x^2-2^2) [/tex] can further be factorised as (x - 2) (x + 2).