If x^2+1/x^2=66,find the value of x^3-1/x^3
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Given , x² + 1 / x² = 66
To find the value of : x³ - 1 / x³
Now , x² + 1 / x² = 66
=> ( x - 1 / x )² + 2. x. 1 / x = 66
[ • ( a )² + ( b )² = ( a - b )² + 2ab → Using this identity ]
=> ( x - 1 / x )² + 2 = 66
=> ( x - 1 / x )² = 66 - 2
=> ( x - 1 / x )² = 64
=> ( x - 1 / x )² = ( 8 )²
=> ( x - 1 / x ) = 8
Thus ,
x³ - 1 / x³
= ( x )³ - ( 1 / x )³
= ( x - 1 / x )³ + 3 . x . 1 / x ( x - 1 / x )
[ • ( a )³ - ( b )³ = ( a - b )³ + 3ab ( a - b ) → Using this identity ]
= ( 8 )³ + 3 × 8 [ • Putting the value of ( x - 1 / x ) ]
= 512 + 24
= 536 [ ★ Required answer ]
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Anonymous:
Ab theek edited ☑ :thumbs_up:
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