Answer: Option d.)
R_eq = (1/R_1 + 1/R_2 + 1/R_3)^-1
Step-by-step explanation:
Since, there are three resistors connected in parallel, the reciprocal of the total resistance of the resistor combination (R_eq) is obtained by adding the reciprocal of each resistance.
i.e 1/R_eq = (1/R_1 + 1/R_2 + 1/R_3)
So, R_eq = (1/R_1 + 1/R_2 + 1/R_3)^-1
Thus, the total resistance (R_eq) is equal to the inverse of the sum of the reciprocal of each resistance.