Question

answer this question fast

Answer 1

a1=3+4×1=7

a2= 3+4×2=11

a3=3+4×3=15

a2-a1

=11-7=4

a3-a2= 15-11=4

As a2-a1=a3-a2

Hence it forms an AP

d=4

a=7

S15=n/2[2a+(n-1)d]

=15/2[2×7+(15-1)4]

=15/2[14+(14×4)]

=15/2(14+56)

15/2×70

=525

Sum of first 15 terms is 525

Hope this helps you

Please mark it as brainliest answer ☺️☺️☺️☺️

Please, please,please, please,please