Question

the sum of the 1st 9 terms is 45 and sum of 18th is 171.what is the 5th term

Answer 1

Answer:

see below :-

Step-by-step explanation:

Let first term = a, common difference = b,

t1 = a , t9 = a + (9–1)*b = a + 8b , according to condition , a+a+8b = 24…..(1),

When we find the sum of first nine terms , we have first term is a , and last term l = a+8b, number of total terms , n= 9,

S = n/2*{a+l} = 9/2*{a +a+8b}. Now putting a+a+8b = 24 from equation (1)

S = (9/2)*24 =108

Answer 2

Answer:

hope this helps you........................