+413 Factorize (81b 4 - 18b 2 + 1).
a. (3b 2 + 1) (3b - 1) (3b + 1)
b. (3b - 1) (3b - 1) (3b - 1) (3b - 1)
c. (b - 1) (9b + 1) (b - 1) (9b + 1)
d. (3b + 1) (3b + 1) (3b - 1) (3b - 1)
+26393 $$\small{\text{Factorize $(81b^4 - 18b^2 + 1)$. }}\\\\$$
$$\small{\text{$
\begin{array}{rcl}
81b^4 - 18b^2 + 1 \\
&=& [9b^2-1]^2 \\
&=& [(3b-1)(3b+1) ]^2\\
&=& (3b-1)^2(3b+1)^2 \\
&=& (3b-1)(3b-1) (3b+1)(3b+1) \\
d. &=& (3b+1)(3b+1) (3b-1)(3b-1) \\
\end{array}
$}}$$
