Answer:
D. Irrational
Step-by-step explanation:

Answer: Associative property
Step-by-step explanation:
No because they are straight lines, they cannot curve to intersect more than once, think of a capital X.
Answer:
The 21st term is 137.
Step-by-step explanation:
Arithmetic progression:
In an arithmetic progression the difference between consecutive terms is always the same, and its called common difference.
The nth term is given by:

In which
is the first term and d is the common difference.
The first two terms are -3, 4.
This means that 
So


The 21st term is

The 21st term is 137.