Ответ:

Rэ = ( ((R1*R2)/(R1+R2) +R3) * (R4+R5) ) / ( (R1*R2)/(R1+R2) +R3+R4+R5 ) +R6

Объяснение:

R12 = (R1*R2)/(R1+R2)

R123 = R12 +R3 = (R1*R2)/(R1+R2) +R3

R45 = R4+R5

R12345 = (R123*R45)/(R123+R45) =

       = ( ((R1*R2)/(R1+R2) +R3) * (R4+R5) ) / ( (R1*R2)/(R1+R2) +R3+R4+R5 )

Rэ = R12345 + R6 =

    = ( ((R1*R2)/(R1+R2) +R3) * (R4+R5) ) / ( (R1*R2)/(R1+R2) +R3+R4+R5 ) +R6