Mathematics

The third and eleventh term of an arithmetic progression are -15 and 25 respectively. Find the:
A.common difference
B.first term
C.number of terms that will give a sum of 30

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2. 👎
3. 👁
1. a11-a3 = 8d = 40
now find a, and then n such that
n/2 (2a+(n-1d)) = 30

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2. 👎

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