Question

13. The second term of an arithmetic sequence is -5, and the third term is 17. What is the first term?A.-22 B.-17 C.-27 D.22

Answer 1

let the first term is 'a'

the second term is (a + d ) = -5 .................(1)

the third term is (a + 2d) = 17 ..................(2)

subtract equation (1) from equation (2)

(a+2d) - (a+d) = 17 -(-5)

a + 2d - a - d = 17 + 5

d = 22

the second term is

a + d = -5

put d = 22

a + 22 = -5

a = -5-22

a = -27

so the answer is first term = -27 that is option C