For what value of the resistor X will the equivalent resistance of the two circuits shown the same-

Options

A. R
B. 6R
C. 2R
D. `sqrt(5-1)/2 R`

Answer

C

Explanation

On comparing both the figures-
`((R + x)(6R))/((R + x) + 6R)`
`x^(2) + xR - 6R^(2) =0`
`x = (-R +- sqrt(R +- sqrt(R^(2) + (4 xx 6R^(2)))/2)) rArr x = (-R + 5R)/2 = 2R`