a) mạch => ((R5ntR3)//R2)ntR4)//R1
=>R532=\(\dfrac{2}{3}\Omega\)
=>RTđ=0,625\(\Omega\)=>\(I=\dfrac{U}{Rtđ}=6,4A\)
Vì R2345//R1=>U2345=U1=U=4V=>\(I1=\dfrac{U1}{R1}=4A\)
R532ntR4=>\(I235=I4=\dfrac{U2345}{R2345}=2,4A\)
R53//R2=>U53=U2=I523.R523=1,6V=>\(I2=\dfrac{U2}{R2}=1,6A\)
R5ntR3=>I5=I3=I35=\(\dfrac{U35}{R35}=\dfrac{1,6}{2}=0,8A\)
Vậy........