Question

if x+1/x=5 then the value of x3-1/x3​

Answer 1

Answer:

Given, x−

x

1

=5

Squaring both the sides,

⇒(x−

x

1

)

2

=5

2

⇒x

2

+

x

2

1

−2(x)(

x

1

)=25

⇒x

2

+

x

2

1

=25+2

⇒x

2

+

x

2

1

=27

Now,

x

3

−

x

3

1

=(x−

x

1

)[(x)

2

+(

x

1

)

2

+(x)(

x

1

)]

=5(27+1)

=140