Cubic

Problem:




$ h(k) = 3k^3 - k + 3 $

Solution:

In general, a cubic equation is hard to solve.
There is a general solution, but it is complicated an a lot of work to do, it is much easier to do with a calculator.

For the first question we can rewrite it into

$ 3k^3 - k + 3 = -75 $

$ 3k^3 - k + 78 = 0 $

Then we can put it into a solver and get it solved.

http://www.1728.org/cubic.htm