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Question: Answered & Verified by Expert
If $f(x)$ is a polynomial of degree $n$ with rational coefficients and $1+2 i, 2-\sqrt{3}$ and 5 are three roots of $f(x)=0$, then the least value of $n$ is
MathematicsQuadratic EquationTS EAMCETTS EAMCET 2004
Options:
  • A $5$
  • B $4$
  • C $3$
  • D $6$
Solution:
1733 Upvotes Verified Answer
The correct answer is: $5$
Since, $(1+2 i),(2-\sqrt{3})$ and 5 are the some roots of polynomial $f(x)$ of degree $n$. As we know this conjugate are also the roots of the polynomial is,
$$
(1-2 i),(2+\sqrt{3})
$$
$\therefore$ The least value of $n$ is 5 .

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