Translate the following into interval notation: "the union of all numbers greater than eight, and less than or equal to negative four".

() is for <>
[] is for ≤≥

greater than 8 means
x>8 or
8 to infinity not counting 8 or
(8,∞)

less than or equal to -4 is
x≤-4 or
from -∞ to -4
or
(-∞,-4]

the infinity has a () sign since you cannot equal infinity, you can approach it

U is unity so

(-∞,-4] U (8,∞)