计算下列各式(0.75a^4b^3c-½a^4b^5-1/10a^3b^2)÷ (-0.5a^3b^2)若x^2+mx-15=(x+3)(x+n),则mn的值为已知ab=9,a-b=-3,则a^2+3ab+b^2的值为

计算下列各式(0.75a^4b^3c-½a^4b^5-1/10a^3b^2)÷ (-0.5a^3b^2)若x^2+mx-15=(x+3)(x+n),则mn的值为已知ab=9,a-b=-3,则a^2+3ab+b^2的值为
计算下列各式(0.75a^4b^3c-½a^4b^5-1/10a^3b^2)÷ (-0.5a^3b^2)
若x^2+mx-15=(x+3)(x+n),则mn的值为
已知ab=9,a-b=-3,则a^2+3ab+b^2的值为

计算下列各式(0.75a^4b^3c-½a^4b^5-1/10a^3b^2)÷ (-0.5a^3b^2)若x^2+mx-15=(x+3)(x+n),则mn的值为已知ab=9,a-b=-3,则a^2+3ab+b^2的值为
(0.75a^4b^3c-½a^4b^5-1/10a^3b^2)÷ (-0.5a^3b^2)
=-1.5abc+ab^3+0.1
若x^2+mx-15=(x+3)(x+n),则mn的值为
3n=-15 m=3+n
m=-2 n=-5
已知ab=9,a-b=-3,则a^2+3ab+b^2=(a-b)^2+5ab=9+45=54