Question

8) The first term of an arithmetic sequence is 6 and the sum of first 15 terms is 450
a) Find the seventh term
b) What is its common difference?
c) Write the algebraic expression

Answer 1

Step-by-step explanation:

a=6

S15 = 450

a7 = ? d= ?

S15 = n/2 (2a + (n-1) d

S15 = 15/2 (2x6 + (15-1) d

450= 15/2 (12+14d)

450 = 7.5(12+14d)

450 = 9+10.5d )

441 = 10.5d

d = 42

a7 = a+6d

a7= 6+6x42

a7 = 258

AP : 6 , 48 , 90 , 132 , 174 , 216,..