Question

find the 15th term from the last term of the arithmetical progression 2,6,10, . . . . . ,86.

Answer 1

2,6,10......,86

if we reverse the AP then it will be:-
86, 82 ...,2
now d= -4
15th term = a+14d
=86+14(-4)
86-56
30=ans.

May this will help you dear

Answer 2

a = 2,
d=6-2 = 4,
l = 86.
l = a + (n-1)d
86 = 2 + (n - 1)4
86 = 2+ 4n - 4
86 = 4n - 2
86 + 2 = 4n
88 = 4n
n = 88/4
n = 22
15th term from the last= (22nd term - 15 the term)from the first = 7th term from the first.
7th term = a + 6d= 2+6*4=2+24=26.
Therefore 15th term from the last is 26.....


Hope this answer helps you.....