a, (R1ntR2)//(R3ntRx)
\(=>U12=U3x=Uab=48V\)
\(=>I3x=\dfrac{U3x}{R3x}=\dfrac{48}{12+18}=1,6A=I3=Ix\)
\(=>U3=I3.R3=1,6.12=19,2V\)
b,\(=>Ix=2I1\)
\(< =>\dfrac{U}{R3x}=2.\dfrac{U}{R12}=>\dfrac{48}{12+Rx}=\dfrac{2.48}{5+15}=>Rx=-2\left(om\right)\)
đề sai à bạn?