Final answer:
The least possible value of the expression 91^2 - 9^2 when two different values from the list 1, 2, 4, and 8 are substituted in any order for the variables 2 and y is 72.
Step-by-step explanation:
The given expression is 912 - 92. According to the question, we need to find the least possible value of this expression when any two different values from the list 1, 2, 4, and 8 are substituted in any order for the variables 2 and y.
Let's substitute the smallest values from the list, 1 and 2, in the expression:
912 - 92 = 81 - 9 = 72
Hence, the least possible value of the expression is 72.