Answer
(a) $f(4)=19$
(b) $f(x+1)= 3x+10$
(c) $f(-x) = -3x+7$
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 $4$ into $x$ to obtain:
$f(4) = 3(4) + 7
\\f(4)=12+7
\\f(4)=19$
(b)
Substitute $x+1$ into $x$ to obtain:
$f(x+1) = 3(x+1)+7
\\f(x+1)= 3x+3+7
\\f(x+1)= 3x+10$
(c)
Substitute $-x$ into $x$ to obtain:
$f(-x) = 3(-x) + 7
\\f(-x) = -3x+7$
