If 
then x2(x2 – 47) = ?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. -1
| Understanding | Application |
| Tricks |
Given
squaring both sides x + 1/x = 9 - 2 x + 1/x = 7 |
| Now |
Again squaring both sides x2 + 1/x2 = 49 - 2 x2 + 1/x2 = 47 |
| Hence |
(x4 + 1)/x2 = 47 x2(x2 - 47) = -1 |