Answer
(a) $f(6)=29$
(b) $f(x+1)= 4x+9$
(c) $f(-x) = -4x+5$
Work Step by Step
RECALL:
$f(a)$ represents the value of the function $f$ when $x=a$.
Evaluate the function by substituting the given value of $x$.
(a)
Substitute $6$ into $x$ to obtain:
$f(6) = 4(6) + 5
\\f(6)=24+5
\\f(6)=29$
(b)
Substitute $x+1$ into $x$ to obtain:
$f(x+1) = 4(x+1)+5
\\f(x+1)= 4x+4+5
\\f(x+1)= 4x+9$
(c)
Substitute $-x$ into $x$ to obtain:
$f(-x) = 4(-x) + 5
\\f(-x) = -4x+5$
