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 Solve: x4 - 13x2 + 42 = 0

Answer»

x4 - 13x2 + 42 = 0

x4 - 7x2 - 6x2 + 42 = 0

⇒ x2(x2 - 7) - 6(x2 - 7) = 0

⇒ (x2 - 7) (x2 - 6) = 0

⇒ (x2 - 7) = 0 or x2 - 6 = 0

⇒ x = \(\pm\sqrt7\) or x = \(\pm\sqrt6\) 

Hence, roots or given equation are -√6, √6, -√7 & √7.



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