Select all the correct answers. Which expression can be factored using the difference of squares identity? 6x^2 - 81
49x - x^4
X^4 - 400
32y^2 - 8z^2
4a^2 - 64b^5

Liz is shipping a package to her friend. the maximum weight of a medium flat-rate box is 20 pounds, including the box which weighs 6 ounces. write and solve an inequality to describe the possible weight in pounds, w, of the contents that liz will ship to her friend if she must use a medium flat-rate box. use the drop-down menus to explain your answer.