I1+I2+I3=0,20I1+6I3=140,5I2+5I3=90求该方程具体步骤怎么求!.
问题描述：
I1+I2+I3=0,20I1+6I3=140,5I2+5I3=90求该方程具体步骤怎么求!.
答
令I3=T ,20I1+6I3=140=>I1=(140-6T)20=7-0.3T ,5I2+5I3=90=>I2=(90-5T)/5=18-T
代入(1) 7-0.3T +18-T+T=0 => 21=0.3T =>T=70 =>I1=-14, I2=-52,I3=70...ANS
答
5(I1+I2+I3)=0
5I2+5I3=90
5I1=-90
I1=-18
20I1+6I3=140
6I3=140+360
I3=250/3
I2=90/5-I3=-196/3