Question

if x+1/x=7 find the value of x³+1/x³​

Answer 1

Answer:

322

Step-by-step explanation:

Cube both sides

$( x + \frac{1}{x} ) {}^{3} = 343 \\ \\ {x}^{3} + \frac{1}{ {x}^{3} } + 3( x .\frac{1}{x} )( x + \frac{1}{x} ) = 343 \\ \\ {x}^{3} + \frac{1}{ {x}^{3} } + 3 \times 7 = 343 \\ \\ {x}^{3} + \frac{1}{ {x}^{3} } = 343 - 21 = 322$

Answer 2

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CUBE BOTH SIDE

$(x + \frac{1}{x}) {}^{3} = 343$

${x}^{3} + \frac{1}{ {x}^{3} } \times + 3 \: (x. \frac{1}{x} )(x + \frac{1}{x} ) = 343$

${x}^{3 } + \frac{1}{ {x}^{3} } + 3 \times 7 = 343$

${x}^{3} + \frac{1}{x {}^{3} } = 343 - 21 = 322$

HENCE..322 IS YOUR ANSWER