若1/R=1/R1+1/R2,则.A:R=R1+R2,B:R=R1+R2/R1+R2,C:R=R1R2/R2+R1,D:R=R1R2/R1-R2求大神帮助

问题描述:

若1/R=1/R1+1/R2,则.A:R=R1+R2,B:R=R1+R2/R1+R2,C:R=R1R2/R2+R1,D:R=R1R2/R1-R2求大神帮助
/是除号

C:R=R1R2/(R2+R1)