Answer:
(y - 4)(y + 4)
Step-by-step explanation:
y² - 16 ← is a difference of squares
Since y² and 16 are both squares separated by a difference , that is minus
A difference of squares factors as
y² - 16
= y² - 4²
= (y - 4)(y + 4)
Answer:
Step-by-step explanation:
Given
Garden: 
One Bag: 
Requires
Determine the number of bags to cover the whole garden
This is calculated as thus;

Expand the numerator



Express 81 as 9²

Evaluate as difference of two squares


Hence, the number of bags is 
Option A is correct answer