%線性方程組的符號解例5.1
syms R1 R2 R3 R4 R5 R6 R7 US
a=sym('[R1+R2+R3,-R3,0;-R3,R3+R4+R5,-R5;0,-R5,R5+R6+R7]')
b=sym('[US;0;0]')
ix=a\b
ix1=simple(ix)
x=subs(ix1,{R1,R2,R3,R4,R5,R6,R7,US},{2,4,12,4,12,4,2,10})
i3=x(1)-x(2)