计算："7/2x^2+6x"-"11-2x^2/9-x^2"+2
问题描述：
计算："7/2x^2+6x"-"11-2x^2/9-x^2"+2
答
7/(2x^2+6x)-(11-2x^2)/(9-x^2)+2
=7/[2x(x+3)]-(11-2x^2)/(3-x)(x+3)+2
=[7(3-x)-2x(11-2x^2)+4x(3-x)(x+3)]/[2x(3-x)(x+3)]
=(21-7x-22x+4x^3+36x-4x^3)/[2x(3-x)(x+3)]
=(7x+21)/[2x(3-x)(x+3)]
=7(x+3)/[2x(3-x)(x+3)]
=7/(6x-2x^2)