Question

Find the sum of the first 20 term of the Series 5+8+11+14+....​

Answer 1

Explanation:

Sn=n/2(2a+(n-1)d). n=20

S20= 20/2 (2x5+(20-1)3 a=5

S20=10(10+57). d=8-5=3

S20=10x67

S20= 670

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