Exams › SSC CGL (Prelims) › General

If x + 3/x = 8, what is the value of x^3 + 27/x^3 ?

1. 440
2. 512
3. 398
4. 480

Correct answer: 440

Solution

With a = x and b = 3/x, ab = 3. Then x^3 + 27/x^3 = (x + 3/x)^3 - 3(3)(x + 3/x) = 8^3 - 9(8) = 512 - 72 = 440.

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