Math, asked by vibhanshu8441, 11 months ago

answer question with photos​

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Answered by Tanuja78827
7

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LovelyG: 27 + 9 = 36, not 39. Please correct it mam!
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Answered by LovelyG
13

Question: If x⁴ + 1/x⁴ = 119, find the value of x³ - 1/x³.

Answer:

\large{\underline{\boxed{\sf x {}^{3}  -  \frac{1}{ {x}^{3} } = 36}}}

Step-by-step explanation:

\large{\underline{\underline{\sf Given \: that :}}}

 \sf  {x}^{4}  +  \frac{1}{ {x}^{4} }  = 119 \\  \\ \bf adding \: 2 \: both \: sides -  \\  \\ \sf ( {x}^{2} ) {}^{2}  +  (\frac{1}{ {x}^{2} } ) {}^{2}  + 2 = 119 + 2 \\ \\ \sf (x {}^{2}) {}^{2}   +  (\frac{1}{x {}^{2} } ) {}^{2}  + 2 \: . \: x {}^{2}  \: . \:  \frac{1}{x {}^{2} }  = 121 \\   \\ \sf (x {}^{2}  +  \frac{1}{ {x}^{2} } ) {}^{2}  = (11) {}^{2}  \\  \\ \sf x {}^{2}  +  \frac{1}{x {}^{2} }  = 11 \\  \\ \bf subtracting \: both \: sides -  \\  \\ \sf x {}^{2}  +  \frac{1}{x {}^{2} }  - 2 = 11 - 2 \\  \\ \sf x ^{2}  +  \frac{1}{ {x}^{2} }  - 2 \: . \: x \: . \:  \frac{1}{x} = 9 \\  \\ \sf (x -  \frac{1}{x}  ) {}^{2}  = (3) {}^{2}  \\  \\ \sf x -  \frac{1}{x}  = 3 \\  \\ \bf Now, on \: cubing \: both \: sides -  \\  \\ \sf (x -  \frac{1}{x}) {}^{3}  =  {(3)}^{3}

[ ∵ (a - b)³ = a³ - b³ - 3ab (a - b)]

 \sf x {}^{3}  -  \frac{1}{ {x}^{3} }  - 3 \:  .\:  x\:.  \:  \frac{1}{x} (x -  \frac{1}{x} ) = 27 \\  \\ \sf x {}^{3}  -  \frac{1}{ {x}^{3} } - 3(3) = 27 \\  \\ \sf x {}^{3}  -  \frac{1}{ {x}^{3} } - 9 = 27 \\  \\ \sf x {}^{3}  -  \frac{1}{ {x}^{3} } = 27 + 9 \\  \\  \boxed{\bf x {}^{3}  -  \frac{1}{ {x}^{3} } = 36}

Hence, the answer is 36.


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