\(\Rightarrow\left\{{}\begin{matrix}a,R1ntR2\Rightarrow Ia=\dfrac{Um}{R1+R2}=\dfrac{9}{12+8}=0,45A\\b,R1nt\left(R2//R3\right)\Rightarrow I2=3I3\Rightarrow I1=I2+I3=4I3\\\Rightarrow I1=\dfrac{4U3}{R3}=\dfrac{4.I1.R23}{R3}\Rightarrow R3=4R23\Rightarrow R3=4.\dfrac{R2R3}{R2+R3}=4.\dfrac{8R3}{8+R3}\Rightarrow R3=24\Omega\\\Rightarrow U2=U23=I1.R23=\dfrac{U}{R1+\dfrac{R2R3}{R2+R3}}.\dfrac{R2R3}{R2+R3}=6V\Rightarrow Ia=\dfrac{U2}{R2}=\dfrac{6}{8}=0,75A\end{matrix}\right.\)
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nãy em chọn lộn môn hoá em xin lỗi ạ :> mọi ngừoi giúp em với em cần gấp ạ
