Question

If x+1/x =7 then find x3+1/x3

Answer 1

Answer:

Step-by-step explanation:x+1/x=7

x+1=7x

7x-x=1

6x=1

x=1/6 then 3x+1/3x= 3×1/6+1/3×1/6=

1/2+1/1/2=3/2/1/2=3 Answer

Answer 2

Step-by-step explanation:

$x + \frac{1}{x} = 7 \\ \\ {x}^{3} + \frac{1}{ {x}^{3} } = ( {x + \frac{1}{x} })^{3} - 3(x + \frac{1}{x} ) \\ = {7}^{3} - 3 \times 7 \\ = 343 - 21 \\ = 322$