In ap..if 12th term is -13 and sum of frst 4 terms is 24,what us thr sum of furst 10 terms??
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[tex]Let a be the first term and d be the common difference.
nth tem of an AP is given by,
a(n) = a + (n - 1)d
and
Sum of n terms is given by,
S(n) = n/2 [2a + (n - 1)d]
Therefore, we have,
a + 11d = -13 ... (1)
and,
sum of 4 terms = 24
4/2 [2a + (n - 1)d] = 24
2 [2a + (n - 1)d] = 24
2[2a + (4 - 1)d = 24
2[2a + 3d] = 24
2a + 3d = 12 ... (2)
Multiplying eq. (1) by 2 we get,
2a + 22d = -26 ... (3)
Now,
Subtratcing eq. (2) by eq. (3), w get,
19d = -38
d = -2
Substituting the value of d in eq. ([/tex]
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