Question

please help! write D u E and D n E using interval notation.

Answer 1

Part 1

$D \cup E$ denotes the union of the two sets (in other words, all the elements in both sets).

This means it is $(-\infty, 4) \cup [7, \infty)$

Part 2

$D \cap E$ denotes the elements shared between both sets.

This means the answer is $(4, 7]$