Question

Find the sum of first 14 numbers of the sequence -3,3,9,15,....​

Answer 1

Answer:

here the 1st term a = -3

common difference d=3-(-3)=3+3=6

sum of the 14 numbers

s=n/2{2a+(n-1)d}

=14/2{2.-3+(14-1).6}

=7{ -6+13.6}

=7{-6+78}

=7{72}

=504