A and B are sets of real numbers defined as follows.

Question

A= {z│z > 4}

B= {z│z ≤ 9}

Write A U B and A ∩ B using interval notation. If the set is empty, write Ø

Answer 1

U means or all the area in both

A U B : {z│z is all real Numbers (lR)} U means or all the area in both

∩ means and common area in both

A ∩ B : {z│4 < z <= 9} (less than equal to for 9) ∩ means and common area

A= {z│z > 4} ( not included

B= {z│z ≤ 9} included ]

Draw number line to help you understand

_____________________ (____________________________________>

4 9

<__________________________________________]_________________

4 9