The sum of the 5th and the 7th terms of an AP is 52 and the 10th term is 46. Find the AP.
Let the first term, common difference be a and d respectively.
As we know
an = a + (n - 1)d
and Given
a5 + a7 = 52
a + 4d + a + 6d = 52
2a + 10d = 52
a + 5d = 26
a = 26 - 5d [ eqn i]
also we have given
a10 = 46
a + 9d = 46
26 - 5d + 9d = 46 [ from eqn i]
4d = 46 - 26
4d = 20
d = 5
using this value in eqn I , we get
a = 26 - 5d
a = 26 - 5(5)
a = 1
as a = 6 and d = 5
So, required AP is a, a + d, a + 2d, a + 3d, …. i.e., 1, 1 + 5, 1 + 2(5), 1 + 3(5), …. i.e., 1, 6, 11, 16, …