Question 142621
A zero of a function is the value of the independent variable ({{{x}}} in these cases) that makes {{{f(x) = 0}}}.


I suspect you may be having some difficulty with function notation, so here is a little tutorial:


{{{f}}}, {{{g}}}, {{{h}}}, and the like are used to represent functions.  {{{f(x)}}} means "the value of the function {{{f}}} at {{{x}}}"  So for your first example, {{{f(x)=x + 5}}}, {{{f(1)=1+5=6}}}, {{{f(2)=7}}}, {{{f(a)=a+5}}}, and so on.  Furthermore, if {{{f(a)=0}}}, then {{{a}}} is a zero of the function.  Your job is to find that value of {{{a}}} for each of your functions so that {{{f(a)=0}}}.


The process is to set the function statement equal to zero and then solve for the variable, thus (for your problem 1):


{{{x+5=0}}}


Add {{{-5}}} to both sides:


{{{x=-5}}}


So, if {{{f(x)=x+5}}} then {{{f(-5)=-5+5=0}}}, therefore {{{-5}}} is a zero of {{{f}}}


Using this method, you should be able to handle the other three problems.