Find the sum of each series, if it exists
91 + 85 + 79 + … + (­29)

651.

Step-by-step explanation:

Note: In the given series it should be -29 instead of 29 because 29 cannot be a term of AP whose first term is 91 and common difference is -6.

Consider the given series is

It is the sum of an AP. Here,

First term = 91

Common difference = 85 - 91 = -6

Last term = -29

nth term of an AP is

where, a is first term and d is common difference.

Sum of AP is

Therefore, the sum of given series is 651.

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step-by-step explanation:

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