The question is looking for the coefficient to the first term after multiplying the two sets of parentheses together.
=(8z − 9)(8z + 9)
using the FOIL method, multiply the first, outside, inside, then last terms
=(8z*8z) + (8z*9) + (-9*8z) + (-9*9)
=64z^2 + 72z - 72z - 81
the middle two terms cancel each other (72-72= 0)
=64z^2 - 81
ANSWER: The value of a is 64
Hope this helps! :)
