Find the maximum value of the function f(x)=x−5 if x is a number between -5 and 13. Select the correct option
A) 6
B) 7
C) 8
D) 9
E) None
Solution:   Since f(x) is a linear function whose slope is 1, a positive number, it is strictly increasing for all x. Therefore its maximal value is reached for the largest value of x, x=13 and f(x)=13-5= 
<gadget id="calculator">13-5</gadget>
<output>8</output>
8.   Answer 8
<result>C</result>
Find the maximum value of the function f(x)=x−5 if x is a number between -5 and 13.