Answers

2016-07-01T18:35:55+08:00
A) Find a1 if a8=72 and d=9

an=a1+(n-1)d
72=a1+(8-1)9
72=a1+63
72-63=a1
9=a1

B) what is the 12th term of the sequence 5,11,17,23...
an=a1+(n-1)d
a12=5+(12-1)6
=5+66
a12=71

C) in the sequence 7,11,15,19... What is the common difference?

an=a1+(n-1)d
19=7+3d
19-7=3d
12=3d
4=d
1 5 1