If distance between 2 molecuels is r then lim `(1)/(r^(x))` will result in which of the following equations to be true/applicable?

Which one of the following is true for x in R:

Show the following equations and check the result. 20-(2r-5)=25

If f R to R is a functin defined by f (x) = x ^(2), then which of the following is true ?

If f:R to R is defined by f(x)=(x^(2)-ax+1)/(x^(2)+ax+1),0ltalt2 , the which of the following is true:

If f:R in R is defined by f(x)=(x^(2)-ax+1)/(x^(2)+ax+1),0ltalt2 , the which of the following is true:

Let E_1 and E_2 denotes gravitational field at distance r_1 and r_2 from the axis of an infinitely long solid cylinder of the radius R. Which of the following must hold true ?