Question

if x + 1/x =5 , find the value of x^3 + 1/x^3​

Answer 1

Answer:

110

Step-by-step explanation:

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

⇒ x + 1 / x = 5

       Cube on both sides:

⇒ ( x + 1 / x )^3 = 5^3

⇒ x^3 + 1 / x^3 + 3( x * 1 / x )( x + 1 / x ) = 125

⇒ x^3 + 1 / x^3 + 3( 1 )( x + 1 / x ) = 125

       x + 1 / x = 5

⇒ x^3 + 1 / x^3 + 3( 5 ) = 125

⇒ x^3 + 1 / x^3 + 15 = 125

⇒ x^3 + 1 / x^3 = 125 - 15 = 110

Answer 2

Step-by-step explanation:

$\bf \underline{\underline{Question}}$

if x + 1/x =5 , find the value of x^3 + 1/x^3

________________________________

$\bf \underline{\underline{Given}}$

• x + 1/x =5
• x^3 + 1/x^3

_______________________________

$\bf \underline{\underline{To..Find}}$

• x^3 + 1/x^3

_______________________________

$\bf \underline{\underline{solution\to}}$

First we solve:-

X- 1/X = 5

putting all values :-

( X- 1/X)³ = (5)³

X³ - 1/X³ - 3 ( X - 1/X ) = 125

X³ - 1/X³ - 3 ( 5 ) = 125

X³ - 1/X³ - 15 = 125

X³ - 1/X³ = 125 + 15 = 140

find the value of x^3 + 1/x^3 = 140