Suppose three complex numbers such that
(α-2)( -2)+|α-2|=2. Also suppose the complex number u such that + + + =0 . Find the smallest integer n : |u|< n
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From the gi \ven equality about (α-2)( α -2)+|α-2|=2 <=> |α-2|=1 => |α|<3 then α 2 u 2 + α 1 u + α 0 =0 <=> u 3 + α 2 u 2 + α 1 u + α 0 =- u 3
=> | α 2 u 2 + α 1 u + α 0 |=| u 3 | through the triangular inequality we have that
| α 2 u 2 |+| α 1 u |+| α 0 | > | u 3 | since |α|< 3
| 3 u 2 | + | 3 u | + 3 > | α 2 u 2 |+| α 1 u |+| α 0 | > | u 3 | =>
| 3 u 2 | + | 3 u | + 3 > | u 3 | <=> | u 3 | - | 3 u 2 | - | 3 u | - 3 < 0 using horners method to factorize the "polynomial" with | u | - 4 (| u | - 4)( | u 2 | + | u | + 1) + 1 < 0 <=> (| u | - 4)( | u 2 | + | u | + 1) < -1 => (| u | - 4)( | u 2 | + | u | + 1) < 0 since ( | u 2 | + | u | + 1) > 0 always | u | - 4 < 0 <=> | u | < 4