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3 votes
if x+
(1)/(x)=
√(11)\\, find the value of
x^(3)+
(1)/(x^(3))

User Awadesh
by
8.2k points

2 Answers

3 votes

Answer:


8 √(11)

if x+(1)/(x)=√(11)\\, find the value of x^(3)+(1)/(x^(3))-example-1
User RajG
by
8.6k points
7 votes

Answer:


8√(11)

Explanation:

Given:


x+(1)/(x)=√(11)

Sum of two squares


\boxed{a^2+b^2=(a+b)^2-2ab}


\textsf{Let}\; a = x


\textsf{Let}\; b = (1)/(x)

Therefore:


\begin{aligned}x^2+(1)/(x^2)&=\left(x+(1)/(x)\right)^2-2x\left((1)/(x)\right)\\\\&=\left(√(11)\right)^2-2\\\\&=11-2\\\\&=9\end{aligned}

Sum of two cubes


\boxed{a^3+b^3=(a+b)(a^2-ab+b^2)}


\textsf{Let}\; a = x


\textsf{Let}\; b = (1)/(x)

Therefore:


\begin{aligned}x^3+(1)/(x^3)&=\left(x+(1)/(x)\right)\left(x^2-x\left((1)/(x)\right)+\left((1)/(x)\right)^2\right)\\\\ &=\left(x+(1)/(x)\right)\left(x^2-1+(1)/(x^2)\right)\\\\&=\left(x+(1)/(x)\right)\left(x^2+(1)/(x^2)-1\right)\\\\&=√(11)\left(9-1\right)\\\\&=8√(11)\end{aligned}

User Tiswas
by
8.6k points

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