Answer:
The first five homologues are generated by adding one - CH2 - at a time, starting with the first homologue CH4.
CH4overset(addCH2−)1st homologue→CH3−CH32nd homologue−→−−−add−CH2CH3−CH2−CH33rd homologue−→−−−−add−CH2−CH3−CH2−CH2−CH34th homologue−→−−−add−CH2CH5−CH2−CH2−CH2−CH35th homologue
By counting carbon and hydrogen atoms in the five homologues we get their molecular formulae as CH4,C2H6,C3H8,C4H10 and C5H12. Comparing these molecular formulae, the following general formula is deduced : CnH2n+2