Ans: (a) $(2m+3)(2m-3)$ (b) $n(2m-3)(m+5)$ (c) $(2m-3)(2m-mn-5n+3)$
-
$\begin{array}{cl}
& 4m^2 – 9 \\
= & (2m)^2 – 3^2\\
= & (2m + 3)(2m – 3)
\end{array}$ -
$\begin{array}{cl}
& 2m^2n + 7mn – 15n \\
= & n (2m^2 + 7m – 15) \\
= & n(2m – 3)(m + 5)
\end{array}$ -
$\begin{array}{cl}
& 4m^2 – 9 – 2m^2n – 7mn + 15 \\
= & (4m^2 – 9) – (2m^2n + 7mn – 15n) \\
= & (2m + 3)(2m – 3) – n(2m – 3)(m + 5) \\
= & (2m – 3)[(2m + 3) – n(m + 5)] \\
= & (2m – 3)(2m + 3 – nm – 5n) \\
= & (2m – 3)(2m – mn – 5n + 3)
\end{array}$
