[" Fiffer "a_(1),a_(2),...,a_(n),...,#" A.P.A.P."],[[" (i) "a_(n)=3+4n," (ii) "a_(n)=9-5n]]

a_(n) = 9-5n, a_(4) = ………….

For an increasing G.P. a_(1), a_(2), a_(3),.....a_(n), " If " a_(6) = 4a_(4), a_(9) - a_(7) = 192 , then the value of sum_(l=1)^(oo) (1)/(a_(i)) is

For an increasing G.P. a_(1), a_(2), a_(3),.....a_(n), " If " a_(6) = 4a_(4), a_(9) - a_(7) = 192 , then the value of sum_(l=1)^(oo) (1)/(a_(i)) is

Show that a_(1),a_(2)"……"a_(n),"……." form an A.P. where a_(n) is defined as below : a_(n)=9-5n

Show that a_(1),a_(2),*a_(n),... form an AP where a_(n) is defined as below: (i) a_(n)=3+4n (ii) a_(n)=9-5n Also find the sum of the first 15 terms in each case.

If a_(1) , a_(2), a_(3) , cdots ,a_(n) are in A.P. with a_(1) =3, a_(n) =39 and a_(1) +a_(2) + cdots +a_(n) =210 then the value of n is equal to

Show that a_(1),a_(2)"……"a_(n),"……." form an A.P. where a_(n) is defined as below : a_(n)=3+4n

if a,A_(1),A_(2),A_(3)......,A_(2n),b are in A.P.then sum_(i=1)^(2n)A_(i)=(a+b)

If a_(1),a_(2),a_(3),...,a_(2n+1) are in A.P.then (a_(2n+1)-a_(1))/(a_(2n+1)+a_(1))+(a_(2n)-a_(2))/(a_(2n)+a_(2))+...+(a_(n+2)-a_(n))/(a_(n+2)+a_(n)) is equal to (n(n+1))/(2)xx(a_(2)-a_(1))/(a_(n+1)) b.(n(n+1))/(2) c.(n+1)(a_(2)-a_(1)) d.none of these

Show that a_(1), a_(2) ,……, a_(n) …. Form an AP where a_(n) is defined as below: (i) a_(n) = 3 + 4n , (ii) a_(n) = 9-5n Also find the sum of the first 15 terms in each case.