যদি x2 + 1/x2 = 38 হয়, তবে x – 1/x = ?

A ±40

B ±6

C ±7

D ±5

Solution

Correct Answer: Option B

প্রদত্ত:
x² + 1/x² = 38

আমরা জানি,
(x - 1/x)² = x² - 2 + 1/x²
অথবা,
x² + 1/x² = (x - 1/x)² + 2

তাই,
(x - 1/x)² + 2 = 38

=> (x - 1/x)² = 38 - 2 = 36

এখন উভয় পাশে বর্গমূল করলে,
x - 1/x = ±6

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