JEE Main 2019 Mathematics question
Let denote the sum of the first n terms of an A.P. If and , then is equal to:
Answer: (A)
Solution
2a + 3d = 8, 2a + 5d = −16 ⇒ d = −12, a = 22; S = 5(44 − 108).
Let denote the sum of the first n terms of an A.P. If and , then is equal to:
2a + 3d = 8, 2a + 5d = −16 ⇒ d = −12, a = 22; S = 5(44 − 108).