Integral values of an algebraic expression

CAT 1997 Slot 1 · QA · Medium · Number System

If nn is an integer, how many values of nn will give an integral value of 16n2+7n+6n\frac{16n^2 + 7n + 6}{n}?

  1. A.

    2

  2. B.

    3

  3. C.

    4

  4. D.

    None of these

Answer

D

Explanation

Rewrite the expression as: 16n2+7n+6n=16n+7+6n\frac{16n^2 + 7n + 6}{n} = 16n + 7 + \frac{6}{n}

Since nn is an integer, 16n+716n + 7 is always an integer. For the whole expression to be an integer, 6n\frac{6}{n} must be an integer.

This implies nn must be an integer factor of 6. The integer factors of 6 are ±1,±2,±3,±6\pm 1, \pm 2, \pm 3, \pm 6.

Thus, there are 8 possible values for nn. Since 8 is not listed in options A, B, or C, the correct choice is None of these.

Practise this under exam conditions

Sign in to solve it with a live timer, the on-screen CAT calculator, and streak and accuracy tracking across every question you attempt.

Solve in the workspace