Question

x+1/x =7 then find the value of x³+1/x³

Answer 1

Sol: If x+1/x =7 then find the value of x3+1/x3 x + 1/x = 7 Cubing on both sides, (x + 1/x)3 = (7)3 x3 + 1/x3 + 3 × x × 1/x × (x + 1/x) = 343 x3 + 1/x3 + 3(7) = 343 x3 + 1/x3 + 21 = 343 x3 + 1/x3 = 343 - 21 x3 + 1/x3 = 322 Therefore, the value of (x + 1/x)3 is 322.

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Answer 2

Given :-

Given :- x + 1 / x = 7

Given :- x + 1 / x = 7To Find :-

Given :-

x + 1 / x = 7

To Find :-

x³ + 1 / x³

Answer :-

322

Solution :-

x³ + 1 / x³

[ • Using identity ]

= ( x + 1/x )³ - 3.x.1/x ( x + 1/x )

[ • Now putting the values ]

= ( 7 )³ - 3 × 1 × 7

= 343 - 21

= 322 [ • Required Answer ]