Math, asked by ancentsaifi, 1 year ago

if x=5 root 2-7,find the value of Xx3-1/Xx3

Answers

Answered by kiki9876
8
refer to the pic for answer
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Answered by sandy1816
2

x = 5 \sqrt{2}  - 7 \\  \\  \frac{1}{x}  =  \frac{1}{5 \sqrt{2} - 7 }  \\   \frac{1}{x}  =  \frac{5 \sqrt{2}  + 7}{50 - 49}  \\  \frac{1}{x}  = 5 \sqrt{2}  + 7 \\  \\ x -  \frac{1}{x}  = 5 \sqrt{2}  - 7 - 5 \sqrt{2}  - 7 \\  =  - 14 \\  \\  {x}^{3}  -  \frac{1}{ {x}^{3} }  = ( {x -  \frac{1}{x} })^{3}  + 3(x -  \frac{1}{x} ) \\  = ( { - 14})^{3}  + 3( - 14) \\  =  - 2744 - 52 \\  =  - 2796

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