The roots of the equation {{x}^{4}}-8{{x}^{2}}-9=0
are
A) \pm 3,\ \pm 1 B) \pm 3,\ \pm i C) \pm 2,\ \pm i D) None of these
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Hi ,
x⁴ - 8x² - 9 = 0
( x² )² - 9x² + 1x² - 9 = 0
[ x² ( x² - 9 ) + 1 ( x² - 9 ) ] = 0
( x² - 9 ) ( x² + 1 ) = 0
Therefore ,
x² - 9 = 0 or x² + 1 = 0
x² = 9 or x² = -1
x = ± √9 or x = ± √ ( - 1 )
x = ± 3 or x = ± i
I hope this helps you.
: )
x⁴ - 8x² - 9 = 0
( x² )² - 9x² + 1x² - 9 = 0
[ x² ( x² - 9 ) + 1 ( x² - 9 ) ] = 0
( x² - 9 ) ( x² + 1 ) = 0
Therefore ,
x² - 9 = 0 or x² + 1 = 0
x² = 9 or x² = -1
x = ± √9 or x = ± √ ( - 1 )
x = ± 3 or x = ± i
I hope this helps you.
: )
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