10,7,4,..............−62
Formulaused
Tn=a+(n−1)d
10,7,4.........−62
a=10
d=7−10=−3
Tn=−62
Tn=a+(n−1)d
−62=10+(n−1)(−3)
⇒−62=10+3−3n
⇒−62−13=−3n
n=25
nthfrom last=n-Tn+1termfrombegining
25−11+1=15thtermfrombegining
T15=10+(15−1)(−3)
=10+(14)(−3)
=10−42
=−32