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  • 10-05-2019
  • Mathematics
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What is the sum of the first 23 terms of the series : 44 + 39 + 34 + 29 + 24 + ....

A. -253
B. -310.5
C. 759

Respuesta :

dhiab
dhiab dhiab
  • 10-05-2019

Answer:

Step-by-step explanation:

the sum: S of arithmetic sequence when the common difference is : d

d= 24-29 = 29-34 =34-39 = 39-44 = -5

S= n/2(A1 + A23)

An =A1+(n-1)d   ....A1 = 44     n = 23

S= 23/2(44 -66   )     .... A23 = 44 +(23-1)(-5) =  44 +22×(-5) =44 - 110 = - 66

S= (23/2)(-22) =23×(-11) = - 253 ......  answer : A

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