$a\text{)}\left(x+2\right)\left(x+2\right)=x^2+2x+2x+4=x^2+4x+4$    

$b\text{)}{\left(5+x\right)}^2=\left(5+x\right)\left(5+x\right)=25+5x+5x+x^2=25+10x+x^2$  

$c\text{)}{\left(x-3\right)}^2=\left(x-3\right)\left(x-3\right)=x^2-3x-3x+9=x^2-6x+9$