Question

the 8th term of an ap is off of its second term and the 11th term exceeds one third of its fourth term by 1 find 15th term

Answer 1

a + 7d = a + d/2

2a + 14d = a + d

a = -13d

a +10d = 1/3(a +3d) + 1

a +10d -1 = 1/3(a + 3d)

3(a + 10d -1) = a +3d

3a + 30d -3 = a+ 3d

2a + 27d =3 2(-13d) + 27d =3(since a = -13d)

-26d + 27d = 3

 d = 3

a= -13d

 a = -39

a + 14d = -39 + 42

 hence a15 =3