Question

In an AP 18,13,8,3,...., S35​

Answer 1

Answer:

Step-by-step explanation:

Sn=n/2(2a+(n-1)d)

a=18

d=a2-a1=13-18=-5

n=35

S35=35/2(2.18+(35-1)-5)

      =35/2(36+(-170))

      =35/2(-134)

      =-35(67)

  S35=-2345

Answer 2

S35=2345

Step-by-step explanation:

a = 18, d= -5

Sn=n/2[2a+(n-1)d]

S35 =35/2[2×18+(35-1)×-5]

       =35/2[36+34×-5]

      =35/2 [36-170]

        =35/2 ×-134

        =35×-67    =2345

Hence, the answer is 2345.

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