Question

If x-1/x=3 find value of x³-1/x³

Answer 1

Answer:

Step-by-step explanation:

x+1/x =3

square both the sides-

x²+1/x² +2 ×x× 1/x =3²

x²+1/x² +2=9

x²+1/x² =7

Now to find value of x³+1/x³ first expand it

x³+1/x³ = (x+1/x) (x²+1/x² -1)

=(3)(7–1)

=3×6

x³+1/x³ =18