Question

(iv) given a = 15, S=125, find d and a
10*​

Answer 1

Answer:

a=15

Sum of ten terms=125

n=10

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

125=10/2[2×15+(10-1)d]

125=5[30+9d]

125/5=30+9d

25=30+9d

25-30=9d

-5=9d

d=-5/9

a10=a+(n-1)d

=15+(10-1)×-5/9

=15+9×-5/9

=15-5=10

last term=10