Math
posted by ReRe on .
Multiply using the rule for the product of the sum and difference of two terms. Assume any variable exponents represent whole numbers.
(x  y + 11)(x  y  11)

Have you learned the rule that they are suggesting that you use? I strongly adise doing so. In this case, what you have is the sum and difference of the terms "xy" and "11".
The general rule is
(a + b) (a  b) = a^2  b^2
Please avoid name changes and the posting of long lists of questions with no work shown.