Question

answer this question​

Answer 1

Step-by-step explanation:

A = 1. An = 81. d = 2

An = a + (n - 1)d

81 = 1 + (n - 1)2

80 = (n - 1)2

40 = n - 1

41 = n

Sn = n/2 ( a + an )

= 41/2 ( 1 + 81 )

= 41/2 ( 82)

= 41 * 41

= 1681

therefore the sum is 1681

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