Question

If the sum of first n terms of an Ap is 2n²+5n then find S20
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Answer 1

Answer:

900

Step-by-step explanation:

Sn = 2n²+5n

So if you want S20

S20 = 2×20² + 5×20

       = 2×400 + 100

       = 800 + 100

       = 900//

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Answer 2

Answer:

900

Step-by-step explanation:

sn = 2n²+5n

S20=2(20)²+5×20

s20=2×400+100

s20=800+100

s20=900