A. Find the sum of the first 60 terms if a1 = 15 and d = 80​

Sagot :

Answer:

142500

Step-by-step explanation:

i used arithmetic sequence calculator

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Answer:

142500

Step-by-step explanation:

Sn=(n/2)[2a1+(n-1)(d)], with n=60 terms

Sn=(60/2)[2(15)+(60-1)(80)]

Sn=(30)[30+(59)(80)]

Sn=(30)[30+4720]

Sn=(30)(4750)

Sn=142500