Question

# Tell whether the sequence 12, 4, -4, -12, -20, .... is arithmetic. Explain your reasoning.

Sequences
Tell whether the sequence 12, 4, -4, -12, -20, .... is arithmetic. Explain your reasoning.

$$d=a_2-a_1=a_3-a_2=...a_n-a_{n-1}$$
$$d=a_2-a_1=a_3-a_2=a_4-a_3=a_5-a_4$$
$$-8=4-12=-4-4=-12+4=-20+12$$