Question

what is the first term in the arithmetic sequence __, 9, __, 33, __, 45
a. -3 b. -1 c. 3 d. 6

Answer 1

Your answer is ----


Let, the AP is

a , 9 , a2 , 33 , a3 , 45 .


we know that difference between two terms is the common difference of the given AP.

So,

9 - a = d .....(1)

45 - a3 = d .....(2)

also,


a3 - 33 = d => -33 + a3 = d ......(3)


adding equation (2) & (3) , we get

12 = 2d

=> d = 12/2

=> d = 6

So, the common difference is 6

put this value in equation (1) , we get

9 - a = d

=> 9 - a = 6

=> a = 9 - 6

=> a = 3



Henec, the first term is 3


Option c. is correct