Bholi's teacher played an important role in changing the course of her life. She was polite and friendly which touched her heart. She encouraged her every time and was affectionate towards her. The teacher transformed her into a confident person who could read, write and speak clearly.This gave her the required confidence. Moreover, teacher’s appreciation and encouragement helped her overcome her low morale.
Assertion (A): The sum of the first fifteen terms of the AP $ 21, 18, 15, 12, \dots $ is zero.
Reason (R): The sum of the first $ n $ terms of an AP with first term $ a $ and common difference $ d $ is given by: $ S_n = \frac{n}{2} \left[ a + (n - 1) d \right]. $
Assertion (A): The sum of the first fifteen terms of the AP $21, 18, 15, 12, \dots$ is zero.
Reason (R): The sum of the first $n$ terms of an AP with first term $a$ and common difference $d$ is given by: $S_n = \frac{n}{2} \left[ a + (n - 1) d \right].$