Question

The nth term an AP is given by 45 - 6n.
What is the sum of its first 15 terms

Answer 1

Step-by-step explanation:

tn=45-6n

first term(t1)=45-6

=39

t2=33

a=39

d=-6

a/q

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

S15=15/2{78+14x-6}

=15/2x-6

=15x-3

=45