If a =16 and b= 5, the value of (a2+ b2+ ab) / (a3 - b3)

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If a =16 and b= 5, the value of (a²+ b²+ ab) / (a³ - b³) is ?

1. 1/11
2. 1/19
3. 121/3971
4. None of these

Correct Option: A

Given Exp. = (a²+ b²+ ab) / (a³-b³)
= 1 / (a - b)
= 1 / (16 - 5)
= 1/11.