One of the most important and exam oriented question from arithmetic progression chapter in which we have been asked to find the 11th term of an AP, if the sum of first q terms of an AP is (63q-3q^2). If its pth term is -60 and also we have to find the value of p.
RS Aggarwal, Class 10, chapter 5C, question no 38.
Sq=63q−3q^2
Tp=−60
S1=a1=63−3=60
S2=a1+a2=63(2)−(34)=114
a1+a1+d=114
d=114−2(60)
=−6
Tp=a+(p−1)d
⇒−60=60+(p+1)(−6)
⇒−120/-6=(p−1)
⇒20=p−1
⇒p=21
T11=a+10d
=60+10(−6)
=0.