Question

B. When two resistors are connected
in series, their effective resistance
is 80 92. When they are connected
in parallel, their effective resistance
is 20 92. What are the values of the
two resistances?​

Answer 1

Answer:

Let R1 and R2 be the two resistances. When they are in parallel, resultant resistance Rp is given by

1/Rp = 1/R1 + 1/R2

Rp = R1R2/(R1 + R2)

2 = R1R2/(R1 + R2)

2(R1 + R2) = R1R2

When they are in series effective resistance  

Rs = R1 + R2

9 = R1 + R2 ⇒ R2 = 9 - R1

2 x 9 = R1 R2

         = R1 (9 - R1)

         = 9R1 - R12.

18 = 9R1 - R12.

R12 - 9R1 + 18 = 0

Solve this quadratic equation. You will get  

R1 = (9 ± √(81 - 4 x 1 x 18))/2

     = (9 ± √9)/2

     =  (9 ± 3)/2

R1 = 3 ohm or 6 ohm

If R1 = 3 ohm, R2 = 6 ohm and vice versa.

Idk is this correct but i guess the numbers are wrong