Chapter 7 - Functions and Graphs - 7.2 Domain and Range - 7.2 Exercise Set - Page 459: 55

$a.\quad-5$ $b.\quad 1$ $c.\quad 21$

$ a.\quad$ $x=-5$ belongs to the interval $x<0$, so we calculate its function value with $f(x)=x$ $f(-5)=-5$ $ b.\quad$ $x=0$ belongs to the interval $x\geq 0$, so we calculate its function value with $f(x)=2x+1$ $f(0)=2(0)+1=1$ $ c.\quad$ $x=10$ belongs to the interval $x\geq 0$, so we calculate its function value with $f(x)=2x+1$ $f(10)=2(10)+1=21$