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If x2 – 3x + 1 = 0, then the value of x6 + x4 + x2 + 1 will be x3
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- 18
- 15
- 21
- 30
- 18
Correct Option: C
x2 – 3 x + 1 = 0
⇒ x2 + 1 = 3 x
⇒ | = 3 | |
x |
⇒ x + | = 3 ........... (i) | |
x |
∴ Expression = | ||
x3 |
Expression = | + | + | + | ||||
x3 | x3 | x3 | x3 |
Expression = x3 + x + | + | ||
x | x3 |
Expression = | x3 + | + | x + | = 2 × 2 = 4 | ||||||
x3 | x |
Expression = | x + | 3 | - 3 . x . | x + | + | x + | |||||||||||
x | x | x | x |
Expression = 33 – 3 × 3 + 3 = 27 – 9 + 3 = 21