If 8k^6+15k^3-2=0, then the positive value of (k + 1/k) is

If 8k^6+15k^3-2=0, then the positive value of (k + 1/k) is : (a) 2(1/2) (b) 2(1/8) (c) 8(1/2) (d) 8(1/8)

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