\[\begin{array}{*{20}{l}}
{a){\kern 1pt} {\kern 1pt} {\kern 1pt} {a^2} + 2ab + {b^2} - 2a - 2b + 1}\\
{{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} = {{(a + b)}^2} - 2.(a + b).1 + 1}\\
{{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} = {{\left( {a + b - 1} \right)}^2}}\\
{b){\kern 1pt} {\kern 1pt} {{(xy + 4)}^2} - {{(2x + 2y)}^2}}\\
{{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} = (xy + 4 + 2x + 2y)(xy + 4 - 2x - 2y)}
\end{array}\]
