I1+I2+I3=0 (1) 5I1-10I3=15 (2)-10I2+10I3=-65 (3)(1)×10+(2)15l1+10l2=153l1+2l2=3 (4)(2)+(3)5l1-10l2=-50l1-2l2=-10 (5)(4)+(5)4l1=-7l1=-7/4l2=(3-3l1)/2=33/8l3=-l1-l2=-19/8
l1=-7 l2=12 l3=-5