(4/9a的4次方b的7次方+1/2a的3次方-1/9a的平方b的6次方)/(-1/3a的三次方)的平方=(4/9a^4b^7+1/2a^3-1/9a^2b^6)/(-1/9a^6)=1/9a^2(4a^2b^7+9/2a-b^6)/(-1/9a^6)=(4a^2b^7+9/2a-b^6)/(-a^4)=(-4a^2b^7-9/2a+b^6)/a^4=-...