Answer: a = 64
if (8z - 9) (8z + 9) = az^2 - b
Firstly, we need to expand the parentheses
[tex]\begin{gathered} (8z-9)(8z+9)=az^2-\text{ b} \\ 8z\cdot8z\text{ + 8z}\cdot9-9\cdot8z\text{ - 9 }\cdot\text{ 9} \\ 64z^2\text{ + 72z - 72z - 81} \\ 64z^2\text{ - 81} \\ \text{ relating the above expression with az}^2\text{ - b} \\ 64z^2-b=az^2\text{ - b} \\ \text{Therefore, a = 64} \end{gathered}[/tex]