Question

In an AP if an 9n²=+5, then find a2

Answer 1

Answer:

We know that,

an=a+(n-1)d

So,a20=a+(20-1)(3)

a20=a+19(3)

a20=a+57

Similarly, a15=a+14d

a15=a+14(3)

a15=a+42

Now,a20-a15=(a+57)-(a+42)

=a+57-a-42

=57-42

=15