Question 702973
For any given value of a then {{{(a+4)}}} and {{{(a+1)}}} are just numbers.


if any combination of numbers when multiplied together results in zero as the answer then one (or more) of the numbers must have been zero.


so if {{{(a+4)(a+1)=0}}} then either {{{(a+4)=0}}} or {{{(a+1)=0}}}
if {{{(a+4)=0}}} then {{{a=-4}}}
if {{{(a+1)=0}}} then {{{a=-1}}}



so there are two solutions: {{{a=-4}}} or {{{a=-1}}}