If x + (1/x) = √3, then find the value of x³ + (1/x)³
Answers
: x - 1 / x = 3. On cubing both sides ; ( x - 1 / x ) = ( 3 )³ Using Identity :
( a - b )³ = a³ - b³ - 3 ab ( a - b ) ⇒ x³ - 1 / x³ - 3 ( x - 1 / x ) = 27. ⇒ x³ - 1 / x³ - 3 ( 3 ) = 27. ⇒ x³ - 1 / x³ - 9 = 27. ⇒ x³ - 1 / x³ = 27 + 9. ⇒ x³ - 1 / x³ = 36.
Answer:
x³ + (1/x)³ = 0
Step-by-step explanation:
Given :- x + (1/x) = √3
To Find :- Value of x³ + (1/x)³
Solution :-
We know that,
a³ + b³ = (a+b)(a²-ab+b²)
( a + b )² = a² + b² + 2ab
⇒ a² + b² = (a+b)² - 2ab
Here, x + (1/x) = √3
x³ + (1/x)³ = (x + (1/x) )( x² - x(1/x) + (1/x)² )
= √3(x² - 1 + (1/x)² )
= √3( (x + (1/x) )² - 2x(1/x) - 1 )
= √3( (√3)² - 2 - 1 )
= √3( 3 - 3 )
= √3 × 0
= 0
Therefore, x³ + (1/x)³ = 0.
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