Question

Find each sequence, find the first 4 terms and the 10th term.

Answer 1

Answer:

Step-by-step explanation:

Sum of the first 4 terms is  

14.50

Explanation:

In an arithmetic sequence, whose first term is  a and difference between a term and its preceding term is  

d ,  the  n t h

term is  a + ( n − 1 ) d and sum of first  

n  terms is  n 2 ( 2 a + ( n − 1 ) d

Hence  6t h  term will be  

a + 5 d = 8  and  10 t h  term will be  a + 9 d = 13

Subtracting first from second,  

4 d = 5  or  d = 1.25 and  a = 8

− 5 ⋅ 1.25 = 8 − 6.25 = 1.75

Hence sum of first four terms is

4 2⋅( 2 ⋅ 1.75 + 3 ⋅ 1.5 ) = 2 ⋅ ( 3.5 + 3.5 ) = 2 ⋅ 7.25 = 14.50