Question

Historical Feature:
In the equation x^3+px+q=o, replace x by H+K. Let 3HK=-p, and show that H^3+K^3=-q

Answer 1

what do you have so far?

Answer 2

this's too bad
just do what it says
I would expand (H+K)^3
and recall we can write the terms 3H^2K as H(3HK)
and 3HK^2 as K(3HK)

Answer 3

and you know that 3HK can be replaced by -p