去括号5c²-（a²-b²-ab）=5c²-a²+b²+ab-m+（-n+p-q)=-m-n+p-qxy-(-2x²-y²+z²）=xy+2x²+y²-z²-（2x-y)+(z-1)=-2x+y+z-1先去括号,再合并同类项5a+(2a-4b)...