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If x = 1 , what will be the value of x3 − – 2x2 – 7x + 5 ? 2 − √3
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- 0
- 2
- 3
- 4
Correct Option: C
| x = | |
| 2 − √3 |
| = | × | ||
| 2 − √3 | 2 + √3 |
| = | × | ||
| 22 − (√3)2 | 4 − 3 |
= 2 + √3
⇒ x – 2 = √3
On squaring both sides,
⇒ (x – 2)2 = (√3)2
⇒ x2 – 4x + 4 = 3
⇒ x2 – 4x + 1 = 0
∴ x3 – 2x2 – 7x + 5 = (x2 – 4x +1) (x + 2) + 3 = 0 + 3 = 3
