Question

help plz..................

Answer 1

a= 2 (given).
We have to find d.
A(n) = a +(n-1)d.
47= 2+(10-1)d.
47-2= 9d.
45=9d.
Therefore d= 45/9 =5.

For the second part
a=2.
d=5.
n=15.
Sum(n)= n/2[2a+(n-1)d].
= 15/2[2*2+(15-1)5].
= 7.5[4+70].
= 7.5*70.
= 525.
Hence sum of first 15 terms will be 525.
Hope this helps.