Question

if 6th term of an ap is -10 and its 10th term is -26,then find its 15th term of an ap

Answer 1

a6 = -10
-10 = a+5d
a10 = -26
-26 = a+9d
d= -4
a=10
a15 = 10+14(-4)
a15=10-56=-46
therefore, the ans. is -46

Answer 2

The given is
a6 = a + 5d = -10. .........(1)
a10 = a + 9d = -26. ........(2)
by solving eqn (1) and (2) we have
a = 10
d = -4
now,
a15 = a + 14d
putting the value of a and d we have
a15 = 10 + 14(-4)
a15 = 10 - 56
a15 = - 46

so the 15th term is -46