If `x_(1),x_(2),….x_(20)` are in H.P then `x_(1)x_(2)+x_(2)x_(3)+….+x_(19)x_(20)`=

If x_(1),x_(2),...x_(2018) are in H.P.,x_(1)x_(2)+x_(2)x_(3)+......+x_(2017)x_(2018)=lambda and x_(1)x_(2018)=mu then the value of ((lambda)/(mu)) is equal to

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) =

Let x_(1), x_(2), …… , x_(n) be in an A.P. If x_(1) + x_(4) + x_(9) + x_(11) + x_(20) + x_(22) + x_(27) + x_(30) = 272 , then x_(1) + x_(2) + x_(3) + ...... + x_(30) is equal to

If x_(1),x_(2),...x_(20) are in H.P.and x_(1),2,x_(20) are in G.P.then sum_(r=1)^(19)x_(r)x_(r+1)=76b.80c.84d none of these

Let x_(1),x_(2),…..,x_(n) be is an AP . If x_(1)+x_(4)+x_(9)+x_(11)+x_(20)+x_(22)+x_(27)+x_(30)= 272 , then x_(1)+x_(2)+x_(3)+…+x_(30) is equal to

If the means of a set of observations x_(1), x_(2),…..x_(10) is 20, then the mean of x_(1)+4, x_(2)+8, x_(3)+12,….x_(10) +40 is

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. prove that x_1x_2+x_2x_3+x_3x_4+……….+x_(n-1)x_n=(n-1)x_1x_n