Question

find sn of the following arithematical geometric sequences 3,12,36,96,240​

Answer 1

Step-by-step explanation:

sn=n/2(2a+(n-1)d)

sn=5/2(2*3+(5-1)9)

sn=5/2(6+36)

sn=5/2(42)

sn=105