Question

The 21st term of an AP whose first two term are -3 and 4 is?

Answer 1

a= -3
d=7
n=21
An=a+(n-1)d
An= -3+(21-1)7
= -3+(20)7
= -3+140
=137
it is easy & simple way
Hope it will help u

Answer 2

here, a=-3
d=7
n=21
an=a+(n-1)*d
-3+(21-1)*7
-3+20*7
-3+140
137