find the sum of the first twenty terms of arthematic series 2+7+2+.. using formula
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Step-by-step explanation:
We know, Sum of n terms is S
n = n/ [2a+(n−1)d]
a= First term =2
d= Common difference =7−2=5
n= number of terms =20
S = 20/2[2(2)+(20−1)5]
S
20
=10[4+95]
S
20
=10(99)
S
20
=990
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