(1)5a^2b*(-2ab^2)^3=5a^2b*(-8)*a^3*b^6=-40*a^5*b^7(2)(12x^3y-20xy)/4xy =12x^3y/4xy -20xy/4xy =3x^2-5二.(m+2n)^2-(m-n)(m+3n)=(m+2n)^2-(m+n-2n)(m+n+2n)=(m+2n)^2-(m+n)^2+4n^2=(m+2n-m-n)(m+2n+m+n)+4n^2=n*(2m+3n)+4n^2=21+2√6还可以吧
^号是什么意思 除么?