Question

Sn=5n2+3n find m if Am=168

Answer 1

Answer:

S1=5(1)²+3(1)

= 5+3

= 8=A

S2 =5(2)²+3(2)

=20+6

=26

S2-S1= A2

26-8=18

D=A2-A

=18-8=10

Am=168

168=A+(M-1)D

168=8+(M-1)10

168=8+10M-10

168=10M-2

168+2=10M

170=10M

M=17 answer