Solution
given that
The nth term of an Ap =4n - 3
an=4n - 3
the 15th term
a15=4×15 - 3
a15=60 - 3
a15=57
Hence the 15th term=57
Find 25th term of an AP whose 10th term is 38 and 14th term is 43
Solution
Let a and d is first term and common diffrerence of AP.
an =last term of AP
According to Question,
10th term is 38
means, a10 = 38
a + (9- 1)d = 38
a + 8d = 38 ............(i)
and 14th term is 43
means, a14 = 43
a + (14-1)d = 43
a + 13d =43 .........(ii)
from equation (i) and (ii)
a + 8d = 38 ............(i)
a + 13d =43 .........(ii)
After solving,
a = 30
d = 1
the 25th term of an AP=
means,
a25 = a + (25 -1)d
a25 = a +24d
a25 = 30+24×1
a25 = 30+24
a25 = 54 Ans........
