The roots of x^3 - 9x^2 + 23x - 15 = 0 are in AP.
x^3 - 9x^2 + 23x - 15 = 0
=> x^3 - 3x^2 - 6x^2 + 18x + 5x - 15 = 0
=> x^2(x -3 ) - 6x ( x - 3) + 5(x - 3) =0
=> (x^2 - 6x + 5)(x - 3) = 0
=> (x^2 - 5x - x + 5)(x - 3) = 0
=> (x(x - 5) - 1(x - 5))(x - 3) = 0
=> (x - 5)(x - 3)(x - 1) = 0
The roots are x = 1, x = 3 and x = 5. They are in AP.
The option (1) has a valid value of one of the roots, 3.
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