1st part is straight forward. for solving any cubic equation, "guess" the 1st solution, then find remaining quadratic factor by long division, or by comparing coefficients. factorise completely to obtain other solutions.

2nd part is rather challenging here. because of the word "hence", have to use results from 1st part.
need to compare 2nd equation to 1st equation to see how they are related. as 2nd equation can be transformed to 1st equation by substituting x with -2/x, so the solutions are similar.

general guide for substitution ...
(a) when some coefficients have change signs, likely the substitution involves -x .
(b) when coefficients have change order, likely the substitution involves reciprocal of x (ie 1/x)
(c) when coefficients have change values , likely the substitution involves some factor times x.

this question is very challenging because it involves (a),(b) AND (c) (ie ALL 3!!)

note that whenever "hence" is used in question, means subsequent part of working must apply results from previous part, otherwise no marks will be awarded for subsequent part even if correct answer.