Question

The function f(x)=5x+4f(x)=5x+4 models the height of a tree, where x represents the years since the tree was planted for year 3 through year 10. What is the practical range of the function?
a.)all real numbers between 3 and 10 inclusive
b.)all integers
c.)all real numbers between 19 and 54 inclusive
d.)integers from 3 to 10 inclusive

Answer 1

"all real numbers between 3 and 10 inclusive" could not be the answer, because these are x-values (values of the independent variable).

"all real numbers between 19 and 54 inclusive" is the range.  Why?  Because in year 3, f(3) = height of tree = 5(3) + 4 = 19 feet.  

In year 10, f(10) = 5(10) + 4 = 54 feet.