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

First solve equation for "q"

--> q = -x^3 -px

then substitute

q = -(H+K)^3 +3HK(H+K)

expand and simplify