Question

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

Answer 1

this is so common do it this is right

Answer 2

6th term of AP is -10
T6=a+(6-1)d
=a+5d=-10 ............(1).
T10=a+(10-1)d
=a+9d=-26 ............(2).
from eq. (2) - (1)........
a+9d-(a+5d)=-26-(-10)
a+9d-a-5d=-26+10
4d=-16
d=-16/4
d=-4
then, a +5d=-10
a+5*-4=-10
a=-10+20
a=10
then, T15=a+(15-1)d
=10+14*(-4)
=10-56
T15 =-46