Question

In an ap the 12 term is -13 and sum of its four terms is 24 find the sum of its first 10 terms

Answer 1

hi dear,
here is ur answer.........................................
according to the question..
a+11d=-13
a=-13-11d.......................................1.
a+a+d+a+2d+a+3d=24
4a+6d=24
2a+3d=12
from eq. 1.
2(-13-11d)+3d=12
-26-22d+3d=12
-19d=38
d=-2
so,
a=-13-11(-2)=-13+22=9
so ,now
sum of ten terms=n/2(2a+(n-1)d)
                           =5(2*9+9*(-2))
                           =5(18-18)
                           =0
hope it helps uh............................
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