Question 209093
m^4 -13m^2 +36 =0
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Let  x= m^2
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x^2 -13x +36 =0
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(x-9)(x-4) =0
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x=9,,,,,,x=4
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but  x=m^2
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m^2 =9,,,,,m= +/- 3
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m^2 = 4,,,,,m= +/- 2
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check,,(+/-3),,,3^4 -13(3^2) +36 =0,,,,,ok
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(+/- 2),,,,2^4 -13(2^2) +36 =0,,,,,ok
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