Can someone please help with these other 2

Part b:
[tex]f(a+3)=(a+3)^2+4[/tex]
Solve for (a+3)^2
[tex]= (a^2+2(3)(a)+3^2)+4[/tex]
[tex]= a^2+6a+13[/tex]
Part c:
[tex]f(d+b)=(d+b)^2+4[/tex]
Solve for (d+b)^2
[tex]= (d^2+2db+b^2)+4[/tex]
[tex]= d^2+2db+b^2+4[/tex]
Let me know if you need any clarifications, thanks!