a. \(R=\dfrac{R1\left(R2+R3\right)}{R1+R2+R3}=\dfrac{6\left(2+4\right)}{6+2+4}=3\Omega\)b. \(U1=U23=U=IR=2.3=6V\)(R1//R23)\(I23=I2=I3=U23:R23=6:\left(2+4\right)=1A\left(R2ntR3\right)\)\(\left\{{}\begin{matrix}U2=I2.R2=1.2=2V\\U3=I3.R3=1.4=4V\end{matrix}\right.\) Câu trả lời: a. \(R=\dfrac{R1\left(R2+R3\right)}{R1+R2+R3}=\dfrac{6\left(2+4\right)}{6+2+4}=3\Omega\)b. \(U1=U23=U=IR=2.3=6V\)(R1//R23)\(I23=I2=I3=U23:R23=6:\left(2+4\right)=1A\left(R2ntR3\right)\)\(\left\{{}\begin{matrix}U2=I2.R2=1.2=2V\\U3=I3.R3=1.4=4V\end{matrix}\right.\)