a-1=0,a=1
b+3=0,b=-3
3c-1=0,c=1/3
那么,(a*b*c)^121/(a^7*b^3*c^4)
=[1*(-3)*1/3]^121/[1^7*(-3)^3*(1/3)^4]
=(-1)^121/(-1/3)
=(-1)*(-3)
=3