$$(a-b); (a+b); =a^{2}-b^{2}$$
$a=b+1\text{, }b\in \mathrm{C}\text{, }c=1$
$a=b+c\text{, }b=-\frac{c}{2}\text{, }c\in \mathrm{C}$
$a=b+1\text{, }b\in \mathrm{R}\text{, }c=1$
$a=b+c\text{, }b=-\frac{c}{2}\text{, }c\in \mathrm{R}$
