Question

Please answer this question as fast as u can

Answer 1

Let the sum of n terms be given by Sn

so

Sn = 3n²/2+ 5n/2

S1 = 3(1)²/2 + 5(1)/2

= 3/2+5/2 = 4

so 1st term is 4 say 'a'

Now

S2 = 3(2)²/2 + 5(2)/2

= 6+5 = 11

Now a2 = S2 - a1

= a2 = 11-4 = 7

Now common difference (d)

= a2-a1 = 7-4 = 3

we know

an = a+(n-1) d

= 4+3n-3

= 1+3n

a20= 4+19×3 =4+57=61

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