Question

If the sum of the first n terms of an AP is 4n-n² find first term,sum of first two terms, second term, 3rd ,10th term and the nth terms

Answer 1

Answer:

Step-by-step explanation:

The sum of first n terms of an A P is

Sn=4n-n²

So first term=4×1-1²=4-1=3

Sum of first two terms=S2=4×2-2²

=8-4=4

Thus second term=4-3=1

Hence common difference =d=1-3=-2

Third term=a+2d=3+2(-2)=3-4=-1

Tenth term=a+9d=3+9(-2)=3-18=-15

nth term=a+(n-1)d

=3+(n-1)(-2)

=3-2n+2

=5-2n

Answer 2

Step-by-step explanation:

The sum of first n terms of an A P is

Sn=4n-n²

So first term=4×1-1²=4-1=3

Sum of first two terms=S2=4×2-2²

=8-4=4

Thus second term=4-3=1

Hence common difference =d=1-3=-2

Third term=a+2d=3+2(-2)=3-4=-1

Tenth term=a+9d=3+9(-2)=3-18=-15

nth term=a+(n-1)d

=3+(n-1)(-2)

=3-2n+2

=5-2n