i suck at algebra help me plz

[Tony Skaloni]

i need some help cause this problem is driving me nuts... the question says by using the definition only compute f ' (1) where f(x) = 1/x^3. Hint: you may need the formula x^3-1 = (x-1)(x^2+x+1) so like i know

F ' (1) = lim 1/x^3 -1
xapp.1 --------------
x-1

then it says the next step should be getting to


1- x^3
----------
x^3(x-1)

i just cannot get to this step for the life of me... can someone plz help me out.

[Darryl_P]

Hint: get a common denominator and then factor the numerator of that limit expression into (1-x)*(1+x+x^2)

[Darryl_P]

OK I see you need more help than that...

note that 1/x^3 - 1

is equal to (1 - x^3) / x^3

[Tony Skaloni]

ah i didn't know that part thank you sir...i'm pretty sure i can do it now