Question

CHAPTER------------AP​

Answer 1

EXPLANASION :-

(4-1/n)+(4-2/n)+(4-3/n)............n

(4-1/n)+(4-2/n)+(4-3/n)............n=4n+(1+2+3+......+n)/n

(4-1/n)+(4-2/n)+(4-3/n)............n=4n+(1+2+3+......+n)/n= 4n+n(n-1)

2*n

=9n-1

2