Prove that `(r_(1) -r)/(a) + (r_(2) -r)/(b) = (c)/(r_(3))`

Show that (b-c)/(r _(1))+ (c-a)/(r _(2))+(a-b)/(r _(3)) =0.

Sum of the first p,q and r terms of an A.P. are a, b and c, respectively. Prove that, (a)/(p) (q-r) + (b)/(q) (r-p) + (c )/(r ) (p-q) = 0

Prove that ((n),(r))+2((n),(r-1))+((n),(r-2))=((n+2),(r))

Two resistors of resistances R_(1)=100pm3 ohm and R_(2)=200pm4 ohm are connected (a) series , (b) in parallel. Find the equivalent resistance of the (a) series combination, (b) parallel combination. Use for (a) the relation R = R_(1)+R_(2) and for (b) (1)/(R') = (1)/(R_(1))+(1)/(R_(2)) and (DeltaR')/(R'^(2)) = (DeltaR_(1))/(R_(1)^(2))+(DeltaR_(2))/(R_(2))

Statement I In a Delta ABC, if a lt b lt c and ri si inradius and r_(1), r_(2) ,r_(3) are the exradii opposite to angle A,B,C respectively, then r lt r_(1) lt r_(2) lt r_(3). Statement II For, DeltaABC r_(1)r_(2)+r_(2)r_(3)+r_(3)r_(1)=(r_(1)r_(2)r_(3))/(r)

Prove that if two bubbles of radii r_(1) and r_(2)(r_(1)ltr_(2)) come in contact with each other then the radius of curvature of the common surface r=(r_(1)r_(2))/(r_(2)-r_(1))

If x=a + (a)/(r ) + (a)/(r^(2)) + …..oo, y= b - (b)/(r ) + (b)/(r^(2))-……..oo and z= c + (c )/(r^(2)) + (c )/(r^(4))+ ….oo then prove that (xy)/(z)= (ab)/(c )

Write ‘True’ or ‘False’ and justify your answer: The volume of the frustum of a cone (1)/(3)pi h(r_(1)^(2)+r_(2)^(2)-r_(1)r_(2)) where h is the vertical height of the frustum and r_(1),r_(2) are the radii of the ends.

Prove that , ""^nP_r = ""^((n-1))Pr + r. ""^(n-1)P_((r-1))

Prove that the greatest value of .^(2n)C_(r)(0 le r le 2n) is .^(2n)C_(n) (for 1 le r le n) .