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x-3-9x-1-0-




Question Number 138835 by mathdanisur last updated on 18/Apr/21
x^3 −9x+1=0
$${x}^{\mathrm{3}} −\mathrm{9}{x}+\mathrm{1}=\mathrm{0} \\ $$
Commented by mr W last updated on 18/Apr/21
x_k =2(√3)sin ((1/3)sin^(−1) ((√3)/( 18))+((2kπ)/3))   k=0,1,2
$${x}_{{k}} =\mathrm{2}\sqrt{\mathrm{3}}\mathrm{sin}\:\left(\frac{\mathrm{1}}{\mathrm{3}}\mathrm{sin}^{−\mathrm{1}} \frac{\sqrt{\mathrm{3}}}{\:\mathrm{18}}+\frac{\mathrm{2}{k}\pi}{\mathrm{3}}\right)\:\:\:{k}=\mathrm{0},\mathrm{1},\mathrm{2} \\ $$
Commented by mathdanisur last updated on 18/Apr/21
Thank Sir
$${Thank}\:{Sir} \\ $$
Commented by mathdanisur last updated on 19/Apr/21
Where did you get it fro can you explain Sir
$${Where}\:{did}\:{you}\:{get}\:{it}\:{fro}\:{can}\:{you}\:{explain}\:{Sir} \\ $$
Commented by mr W last updated on 19/Apr/21
see Q89687
$${see}\:{Q}\mathrm{89687} \\ $$
Commented by Dwaipayan Shikari last updated on 19/Apr/21
Coincidence ! same kind of question asked in same dates.  One year interval!
$${Coincidence}\:!\:{same}\:{kind}\:{of}\:{question}\:{asked}\:{in}\:{same}\:{dates}. \\ $$$${One}\:{year}\:{interval}! \\ $$

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