Answer
See below.
Work Step by Step
According to the exercise:
$a_1=1,a_2=4$
$a_3=a_2-a_1=4-1=3$
$a_4=a_3-a_2=3-4=-1$
$a_5=a_4-a_3=-1-3=-4$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.