Answer:
a9=20
Step-by-step explanation:
an=3n-7
a1=3(1)-7
=3-7
=-4
a2=3(2)-7
=6-7
=-1
a3=3(3)-7
=9-7
=2
a=-4....a2=-1....a3=2
d=a2-a1
=3
a9=a+(n-1)d
=-4+(9-1)3
=-4+8(3)
=-4+24
=20..
