Ans: (a) $(3c-1)^2$ (b) $(7c+d-1)(c+d+1)$
-
$\begin{array}{cl}
& 9c^2-6c+1 \\
= & (3c)^2 -2(3c) +1^2 \\
= & (3c-1)^2
\end{array}$ -
$\begin{array}{cl}
& (4c+d)^2 -9c^2+6c-1\\
= & (4c+d)^2 -(9c^2-6c+1) \\
= & (4c+d)^2 -(3c-1)^2 \\
= & [(4c+d)+(3c-1)][(4c+d)-(3c-1)] \\
= & (7c+d-1)(c+d+1)
\end{array}$
