Question

Uhll-starmelic progression)
1. The sum of first k terms of A.P. is 2k? + 3k, find its 2nd term.
2. Determine the A.p whose 4th term is 18 and difference of 9h and 15h term is 30.​

Answer 1

Step-by-step explanation:

2. a4=18

a9-a15=30

a+(9-1)d-{a+(15-1)d}=30

a+8d-a-14d=30

-6d=30

d=-5

Now, a4=18

a+(4-1)(-5)=18

a+(3)(-5)=18

a-15=18

a=33

Therefore the AP is 33, 28, 23.........