#### Answer

(a) First gap: square
Second gap: add 3
(b) When $x=2$, $f(x)=7$
When $x=4$, $f(x)=3$
When $x=6$, $f(x)=7$

#### Work Step by Step

(a) Subtract 4, then square and add 3.
(b) When $x=2$ $$f(2)=(2-4)^{2}+3=(-2)^{2}+3=4+3=7$$.
When $x=4$ $$f(4)=(4-4)^{2}+3=0^{2}+3=3$$.
When $x=6$ $$f(2)=(6-4)^{2}+3=2^{2}+3=4+3=7$$.