1.[(2a+b)(2a-b)-4(a-2b)^2+4b(a-2b)]÷(-4b)=[4a^2-b^2-4a^2+16ab-16b^2+4ab-8b^2]/(-4b)=(20ab-25b^2)/(-4b)=25b/4-5a2.[(-3mn)^2×m^3-2m^3(3mn^2)^3*1/2n]÷（-3m^3n)^2=(9m^5n^2-3m^4n^7)/(9m^6n^2)=1/m-n^5/3m...