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If x4 + 1 = 119, and x > 1, then find the positive value of x3 - 1 . x4 x3
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- 25
- 27
- 36
- 49
- 25
Correct Option: C
x4 + | = 119 | |
x4 |
⇒ | ![]() | x2 + | ![]() | 2 | - 2 = 119 | |
x2 |
⇒ | ![]() | x2 + | ![]() | 2 | = 119 + 2 = 121 | |
x2 |
⇒ | ![]() | x2 + | ![]() | 2 | = (11)2 | |
x2 |
⇒ x2 + | = 11 | |
x2 |
⇒ | ![]() | x - | ![]() | 2 | + 2 = 11 | |
x |
⇒ | ![]() | x - | ![]() | 2 | = 11 - 2 = 9 = 32 | |
x |
⇒ x - | = 3 | |
x |
On cubing both sides,
⇒ | ![]() | x - | ![]() | 3 | = 27 | |
x |
⇒ x3 - | - 3x. | ![]() | x - | ![]() | = 27 | |||
x3 | x | x |
⇒ x3 - | - 3 × 3 = 27 | |
x3 |
⇒ x3 - | = 27 + 9 = 36 | |
x3 |