Question

The third term and the ninth term of an arithmetic sequence are 7.5 and -7.5respectively.find the first term and the common difference of the series

Answer 1

Answer:

d= -2.3, a= 13.1

Step-by-step explanation:

t3= 7.5

t9= -7.5

a+2d = 7.5 (I)

a+ 8d= -7.5 (2)

solving equations 1 and 2

d= -2.3

Putting value of d in eqn 1

a+ 2* (-2.3) = 7.5

a -5.6= 7.5

a= 7.5 + 5.6

a= 13.1