If `x_1,x_2,x_3….,x_n` are in H.P. prove that `x_1x_2+x_2x_3+x_3x_4+……….+x_(n-1)x_n=(n-1)x_1x_n`

If x_(1),x_(2),x_(3)...x_(n) are in H.P,then prove that x_(1)x_(2)+x_(2)x_(3)+xx x-3x_(4)+...+x_(n-1)x_(n)=(n-1)x_(1)x_(n)

If x_(1), x_(2), x_(3) .................x_(n) are in H.P.then x_(1)x_(2)+x_(2)x_(3)+.......+x_(n-1)x_(n) =

If x_(1),x_(2),x_(3),"……" are in A.P., then the value of 1/(x_(1)x_(2))+1/(x_(2)x_(3))+1/(x_(3)x_(4))+"……"1/(x_(n-1)x_(n)) is :

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)

Each of the numbers x_(1),x_(2),x_(3),...x_(n),n>=4 is equal to 1 or -1. Suppose x_(1)x_(2)x_(3)x_(4)+x_(2)x_(3)x_(4)x_(5)+x_(3)x_(4)x_(5)x_(6)+....x_(n-3)x_(n-2)x_(n-1)x_(n)+x_(n-2)x_(n-1)x_(n)x_(1)+x_(n-1)x then

If x_(1),x_(2),x_(3),x_(n) are the roots of x^(n)+ax+b=0 then the value of (x_(1)-x_(2))(x_(1)-x_(3))(x_(1)-x_(4))......(x_(1)-x_(n)) is equal to