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    If m and n are not prime to each other, the possible number of common roots of the equations xm−1=0,xn−1=0x^m-1=0, x^n-1=0xm−1=0,xn−1=0 is​
    Question

    If m and n are not prime to each other, the possible number of common roots of the equations xm1=0,xn1=0x^m-1=0, x^n-1=0 is​

    A.

    more than one

    B.

    one

    C.

    0

    D.

    two

    Correct option is A

    Given:
    Two equations:
    xm1=0,xn1=0x^m-1=0, x^n-1=0​​
    And m and n are not coprime, i.e., they have a common factor greater than 1.

    Formula:
    The number of common roots = number of solutions to xd - 1 = 0, where d = GCD of m and n

    Solution:

    The roots of  xm1=0x^m-1=0​ are the m-th roots of unity (complex numbers on the unit circle spaced evenly).

    Similarly, xn1=0 x^n-1=0​ has n-th roots of unity.

    If m and n are not coprime, then GCD(m, n) = d > 1

    Therefore, both equations have all the d-th roots of unity in common.

    This means the number of common roots is more than one — exactly d in number.

    Final Answer:
    The possible number of common roots is more than one

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