if the sum of first n term is 4n-n2, what is the first term what is the sum of first two terms also find the 3 and n terms

We have,Sn = 4n - n2Sn-1 = 4n-1 - n-12 = 4n - 4 - n2 + 1 - 2n = 4n-4-n2-1+2n = 6n-5-n2Now, an = Sn  - Sn - 1an = 4n-n2 - 6n - 5 - n2an = 4n-n2-6n+5+n2an = 5-2nNow, first term, a1 = 5 - 2 × 1 = 5 - 2 = 3Now, sum of first 2 terms, S2 = 4× 2 - 22 = 8 - 4 = 4Now, a3 = 5 - 2 × 3 = 5 - 6 = -1Now, nth term, an = 5 - 2n

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First term is 3
sum of two terms is 7
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FIRST TERM IS 3
SUM OF SECOND TERM IS 7  
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this is 10th std arthmatic progression chap question
ap = a + (n-1)d
Substitute the values and u will get the answer
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