Ans: (a) $x^2(x+y-7)$ (b) $(x-1)(x+1)(x+y-7)$
-
$\begin{array}{cl}
& x^3 +x^2y -7x^2 \\
= & x^2(x + y -7)
\end{array}$ -
$\begin{array}{cl}
& x^3 +x^2y – 7x^2 -x-y+7 \\
= & x^2(x+y-7) – (x+y-7) \\
= & (x+y-7)(x^2-1) \\
= & (x+y-7)(x+1)(x-1)
\end{array}$
