Question

if x plus one by x square is equal to 3 then x cube + 1 y cube is equal to

Answer 1

x+1/x  = 3

cube on both sides,

(x+1/x)^3 = 3^3

by formula (a+b)^3 = a^3 +b^3+3ab(a+b)

here,

x^3 +1/x^3 + 3(x*1/x)(x+1/x)  = 3^3

x^3 +1/x^3 +3(3) = 27

x^3 +1/x^3 = 27-9

x^3 +1/x^3 = 18


i hope this will help you


-by ABHAY

Answer 2

Hlo friend.. Cutiepie Here..

Here is ur answer :

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

To find

${x}^{3} + \frac{1}{ {x}^{3} }$


Let a = x

Let b = 1/x

Using identity,

( a + b)³ = a³ + b³ + 3ab( a + b)

Cube on both sides in eqⁿ (1)

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


${x}^{3} + \frac{1}{ {x}^{3} } + 3 \times x \times \frac{1}{x} (x + \frac{1}{x}) = 27$

${x}^{3} + \frac{1}{ {x}^{3} } + 3(3) = 27$


${x}^{3} + \frac{1}{ {x}^{3} } + 9 = 27$


${x}^{3} + \frac{1}{ {x}^{3} } = 27 - 9$


${x}^{3} + \frac{1}{ {x}^{3} } = 18$


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HOPE IT HELPS..