If x4 + x-4 = 2599, then one of the values of x - x-1, where x > 0, is equal to :
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 7
| Understanding | Application |
| Given |
x4 + x-4 = 2599 ⇒ {(x2)2 + (x-2)2} = 2599 ⇒ (x2 + x-2)2 - 2 = 2599 ⇒ (x2 + x-2)2 = 2599 + 2 ⇒ (x2 + x-2)2 = 2601 ⇒ x2 + x-2 = 51 |
| Now |
⇒ x2 + x-2 = 51 ⇒ (x - x-1)2 + 2 = 51 ⇒ (x - x-1)2 = 51 - 2 ⇒ (x - x-1)2 = 49 |
| Hence | ⇒ x - x-1 = 7 |