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If x = ³√28 , y = ³√27, then the value of x + y – 1 is x2 + xy + y2
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- 8
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- 6
- 5
Correct Option: C
x = ³√28
∴ x3 = (³√28)3 = 28
Again, y = ³√27
∴ y3 = (³√27)3 = 27
| ∴ Expression = (x + y) – | |
| x2 + xy + y2 |
| = (x + y) – | |
| (x – y)(x2 + xy + y2) |
| = (x + y) – | |
| x3 – y3 |
| = (x + y) – | |
| 28 – 27 |
= x + y – x + y
= 2y = 2 × ³√27 = 2 × 3 = 6
