If $\alpha ,\beta$ are the roots of $x^2 -ax + b = 0$ and if $\alpha^n + \beta^n = V_n$, then -

  • A

    $V_{n+1} = aV_n + bV_{n-1}$

  • B

    $V_{n+1} = aV_n + aV_{n-1}$

  • C

    $V_{n+1} = aV_n -bV_{n-1}$

  • D

    $V_{n+1} = aV_{n-1} -bV_n$

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