Question

if the sum of the first 'n' terms of an A. P is 4n-n², what is the first term (remember the first term is s1) What is the sum of first two terms? what is the second term. similarly find the 3rd,10th, and nth terms ​

Answer 1

Answer:

Sn=4n-n^2

a1=>S1=4(1)-(1)^2

=4-1=3

a2=4(2)-(2)^2

=8-4=4

d=a2-a1=4-3=1

S2=2/2[2(3)+(2-1)1]

=1[6+1]=7

Answer 2

first term 3 , second term 1 , third term -1 , 10th term = -15

Step-by-step explanation:

sum of the first 'n' terms of an A. P is 4n-n²

sum of 1st term = 1st term

s1 = 4×1 - 1^2 = 3

fiirst term = 3

sum of 1st two terms = 4×2 - 2^2 = 4

4 = first term + 2nd term

4 = 3 + 2nd term

2nd term = 1

so AP is

3 , 1 and so on

d = -2

3rd term = -1

10th term = 3 + 9×(-2) = -15

first term 3 , second term 1 , third term -1 , 10th term = -15

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