a) 1/Rc = (1/R1) + (1/R2) or B) Rc = (R1 x R2)/ (R1 + R2)

2) Given R1=R ohms(a real physical resistor) and R2 is a negative resistor =-R ohms

Then from a) 1/Rc = (1/R) + (1/-R) = (1/R) - (1/R) = 0 and

__Rc = 1/0__

Or from B) Rc = (R x -R)/ (R-R)

__= - (R squared)/0__

The results for Rc are different so what is wrong?