Step-by-step explanation:
The given expression is
[tex]\frac{f(b)-f(a)}{b-a}=2[/tex]
Notice that [tex]a[/tex] and [tex]b[/tex] are elements of the domain and [tex]f(a)[/tex] and [tex]f(b)[/tex] are elements of the range.
Observe the notation used, an element of the range is always written like [tex]f(x)[/tex] where [tex]x[/tex] is an element of the domain.
Also, notice that this expression is using two pair of coordinates, which are [tex](a, f(a))[/tex] and [tex](b,f(b))[/tex].
On the other hand, the definition of average rate of change is
[tex]r=\frac{y_{2} -y_{1} }{x_{2}-x_{1} }[/tex]
Where [tex](x_{1} ,y_{1} )=(a ,f(a))[/tex] and [tex](x_{2} ,y_{2} )=(b ,f(b))[/tex].
Having said that, the given expression represents an average rate of change in the interval, where the rate is 2. The right answer is the third option.