the 9th term of an ap is -32 and the sum of its 11th and 13 term is minus 94 find the common difference of AP
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Answer:
Step-by-step explanation:
nth term of AP, tₙ = a + (n - 1)d
9th term, t₉ = a + 8d
11th term, t₁₁ = a + 10d
13th term, t₁₃ = a + 12d.
Given,
a + 8d = - 32 ------ (1)
a + 10d + a + 12d = -94
=> 2a + 22d = - 94
=> a + 11d = - 47 -------------- (2)
a + 11d = - 47
a + 8d = - 32
- - +
------------------
3d = - 15
d = -5
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