binomial question (1 Viewer)

[live.fast]

Expand (x - (1/x) ) ^ 3 in ascending powers of x



????

 

[ellen.louise]

Expand (x - (1/x) ) ^ 3 in ascending powers of x



????

ok...


=(x - (1/x))(x^2 - 2 + (1/x^2))
=x^3 - 2x + 1/x - x + 2/x - 1/x^3
=x^3 - 3x + 3x^-1 - x^-3
= - x^-3 + 3x^-1 - 3x + x^3

Ascending powers of x is just the order you arrange it in at the end.

 

[pLuvia]

Using binomial
(x-(1/x)³
=(3C0*(-1/x)³+3C1*x*(-1/x)²+3C2*x²*(-1/x)+3C3*x³)

Simplify