(3x+9)(6x+8) (3x+7y)(3x-7y) (1/3a^2b^2)(-15a^2b^2) (3mn+1)(3mn-1)-8m^2n^2 (x+2)^2-(x+1)(x-1)(x+y+z)(x+y-z)(1)(3x+9)(6x+8) (2)(3x+7y)(3x-7y) (3) (1/3a^2b^2)(-15a^2b^2) (4)(3mn+1)(3mn-1)-8m^2n^2 (5) (x+2)^2-(x+1)(x-1) （6)（x+y+z)（x+y-z） 上面的有点不清晰这才是
问题描述：
(3x+9)(6x+8) (3x+7y)(3x-7y) (1/3a^2b^2)(-15a^2b^2) (3mn+1)(3mn-1)-8m^2n^2 (x+2)^2-(x+1)(x-1)
(x+y+z)(x+y-z)
(1)(3x+9)(6x+8) (2)(3x+7y)(3x-7y) (3) (1/3a^2b^2)(-15a^2b^2) (4)(3mn+1)(3mn-1)-8m^2n^2 (5) (x+2)^2-(x+1)(x-1) （6)（x+y+z)（x+y-z） 上面的有点不清晰这才是
答
(1)(3x+9)(6x+8)=18x^2+24x+54x+72=18x^2+78x+72(2)(3x+7y)(3x-7y) =9x^2-49y^2(3) (1/3a^2b^2)(-15a^2b^2) =(-15a^2b^2)/(3a^2b^2)=-15/3=-5(4)(3mn+1)(3mn-1)-8m^2n^2 =9m^2n^2-1-8m^2n^2=m^2n^2-1(5) (x+2)^2-(x+...