Question 678888
You never said what function you have. Thus nobody can tell you what to do exactly.

From your answer to part (a) I expect that you could factor your function into a form like:

{{{y = C(x+1)(x-5)}}}

If so, then when you replace y with zero, you have a multiplication of 3 factors that equals zero. As C is a non-zero number, remain only 2 factors that can be zero: either {{{x+1=0}}}, or {{{x-5=0}}}.