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If x + 1/x = 9, then the value of x^2 + 1/x^2 is ______. - Mathematics

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Question

If `x + 1/x = 9`, then the value of `x^2 + 1/x^2` is ______.

Options

  • 77

  • 79

  • 83

  • 85

MCQ
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Solution

If `x + 1/x = 9`, then the value of `x^2 + 1/x^2` is 79.

Explanation:

If `x + 1/x = 9`, we need to find the value of `x^2 + 1/x^2`.

Step 1: Square both sides of the equation:

`(x + 1/x)^2 = 9^2`

`x^2 + 2 + 1/x^2 = 81`

Step 2: Subtract 2 from both sides:

`x^2 + 1/x^2 = 81 - 2`

`x^2 + 1/x^2 = 79`

Therefore, the value of `x^2 + 1/x^2` is 79.

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Chapter 3: Expansions - Exercise 3C [Page 74]

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Nootan Mathematics [English] Class 9 ICSE
Chapter 3 Expansions
Exercise 3C | Q 6. | Page 74
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