- 真可
-
1.(a+b)^2-9
=(a+b)^2-3^2
=(a+b-3)(a+b+3)
2.4(3x+2y)^2-9(x-y)^2
=[2(3x+2y)]^2-[3(x-y)]^2
=(6x+4y)^2-(3x-3y)^2
=(6x+4y-3x+3y)(6x+4y+3x-3y)
=(3x+7y)(9x+y)
- 可可
-
1.(a+b)^2-9 =(a+b+3)(a+b-3)
2.4(3x+2y)^2-9(x-y)^2
=[2(3x+2y)+3(x-y)][2(3x+2y)-3(x-y)]
=(9x+y)(3x+7y)
- 小菜G
-
(a+b)^2-9=(a+b+3)(a+b-3)
4(3x+2y)^2-9(x-y)^2
=[2(3x+2y)+3(x-y)][2(3x+2y)-3(x-y)]
=(9x+y)(3x+7y)
- 苏萦
-
1.(a+b)^2-9
=(a+b+3)(a+b-3)
2.4(3x+2y)^2-9(x-y)^2
=(6x+4y+3x-3y)(6x+4y-3x+3y)
=(9x+y)(3x+7y)