(a²+ab/-c)³÷(a²-b²/-ac)^4=-[a(a+b)/c]³÷[(a+b)(a-b)/(ac)]^4
=-a³(a+b)³*a^4*c/[(a+b)^4(a-b)^4]
=-a^7c/[(a-b)^4(a+b)]