" If "x_(1),x_(2),...,x_(n)" are in H.P,then "sum_(r=1)^(n-1)x_(r)x_(r+1)" is equal to "

Q.if x_(1),x_(2)......x_(n) are in H.P. then sum_(r=1)^(n)x_(r)x_(r+1) is equal to :(A)(n-1)x_(1)x_(n)(B)nx_(1)x_(n)(C)(n+1)x_(1)x_(n)(D)(n+2)x_(1)x_(n)

If x_(1),x_(2),x_(3),......x2_(n) are in A.P, then sum_(r=1)^(2n)(-1)^(r+1)x_(r)^(2) is equal to

Q. if x_1,x_2......x_n are in H.P ., then sum_(r=1)^n x_r x_(r+1) is equal to : (A) (n-1)x_1 x_n (B) n x_1 x_n (C) (n+1)x_1 x_n (D) (n+2)x_1 x_n

lim_(xto1) (sum_(r=1)^(n)x^(r)-n)/(x-1) is equal to

A , r = 1 , 2, 3 ….., n are n points on the parabola y^(2)=4x in the first quadrant . If A_(r) = (x_(r),y_(r)) where x_(1),x_(2),….x_(n) are in G.P and x_(1)=1,x_(2)=2 then y_(n) is equal to

A , r = 1 , 2, 3 ….., n are n points on the parabola y^(2)=4x in the first quadrant . If A_(r) = (x_(r),y_(r)) where x_(1),x_(2),….x_(n) are in G.P and x_(1)=1,x_(2)=2 then y_(n) is equal to

lim_(xrarr1) (sum_(x=1)^(n)x^(r)-n)/(x-1) is equal to

The value of sum_(x=1)^(n)(-1)^(r+1)(C(n,r))/(r+1) is equal to