14. If the sum of first 8 terms of arithmetic progressions is 136 and that of first 15 terms is 465, then
find the sum of first 25 terms.
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Step-by-step explanation:
First, make 2 equations from the given conditions. Then, solve the 2 equations to get first term(a) and common difference(d).
At last, find the sum of 25 numbers
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