1/R=1/R1+ 1/R2 |*R*R1*R2
R1R2=RR2+RR1
R1R2=R(R2+R1) | : (R2+R1)
R1R2/(R2+R1)=R
1/R=1/R1+ 1/R2 |*R*R1*R2
R1R2=RR2+RR1
R1R2-RR1=RR2
R1(R2-R)=RR2 | : (R2-R)
R1= RR2/R2-R
2/a=3/b-4/c |*a*b*c
2bc=3ac - 4ab
2bc=a(3c-4b) | : (3c-4b)
a= 2bc/3c-4b
2/a=3/b-4/c |*a*b*c
2bc=3ac - 4ab
4ab=3ac-2bc
4ab=c(3a-2b) | : (3a-2b)
c=4ab/3a-2b