Solve: x^6 - 6x^5 + 10x^4 -9x^2 + 6x - 2 = 0 given that (2 + √3) and (1 + i) are roots.
Solve: x6 - 6x5 + 10x4 -9x2 + 6x - 2 = 0 given that (2 + √3) and (1 + i) are roots.
1 Answers
(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.