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Solve: x6 - 6x5 + 10x4 -9x2 + 6x - 2 = 0 given that (2 + √3) and (1 + i) are roots. |
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Answer» (2 + √3) and (1 + i) are roots of equation. x6 - 6x5 + 10x4 -9x2 + 6x - 2 = 0-------(i) Let p(x) = x6 - 6x5 + 10x4 - 9x2 + 6x - 2 \(\because\) (2 + √3) and (1 + i) are roots of equation (i) \(\therefore\) (2 + √3) and (1 - i) are roots of equation (i) ⇒ (x - (2 + √3))(x - (2 - √3)) is a factor of p(x) ⇒ ((x - 2) - √3) ((x - 2) + √3) is a factor of p(x) ⇒ ((x - 2)2 - 3) is a factor of p(x) ⇒ (x2- 4x + 1) is a factor of p(x) Now, \(\frac{P(x)}{x^2-4x + 1}=\frac{x^6-6x^5+10x^4-9x^2+6x-2}{x^2-4x+1}\) =(x4- 2x3 + x2 + 6x + 14) (x2- 4x + 1) + \(\frac{56x-16}{x^2-4x+1}\) \(\therefore\) x2 - 4x + 1 is not a divisior of p(x). \(\therefore\) (2 +√3) is not a root or given equation. \(\therefore\) (1 + i) is a root of equation (i) \(\therefore\) (x - (1 + i))(x - (1 - i)) is a factor of P(x) ⇒ ((x - 1)2 - i2) is a factor of P(x) ⇒ (x2- 2x + 2) is a factor of P(x) Now, \(\frac{P(x)}{x^2-2x + 2}\) = \(\frac{x^6-6x^5+10x^4-3x^2+6x-2}{x^2-2x+2}\) = x4 - 4x3 + 8x + 7 + \(\frac{4x-16}{x^2-2x+2}\) Hence, x2 - 2x + 2 is not a divisior of P(x). \(\therefore\) (1 + i) is not a root given equation. |
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