7年级数学题36

来源：百度知道 编辑：UC知道 时间：2024/06/24 16:06:37
全要过程(a+1)(a-1)(a的2方-1）=过程
（x-2)(x+2)(x的2方+4）=过程
（x+3y)的2方+2（x-y)(x+y)+(x-3y)的2方
[（a-1/2)的2方+（a+1/2)的2方]（2a的2方-1/2）
（a+2b-3)(a+2b+3)=
（x的2方+x+3)(x的2方-x-3)
(x+2y+3)的2方-（x-2y+3)(x-2y-3)=

(a+1)(a-1)(a^2-1）=(a^2-1)^2=a^4-2a^2+1

（x-2)(x+2)(x^2+4）=(x^2-4)(x^2+4)=x^2-16

（x+3y)^2+2（x-y)(x+y)+(x-3y)^2
=x^2+6xy+9y^2+2x^2-2y^2+x^2-6xy+9y^2
=4x^2-16y^2

[（a-1/2)^2+（a+1/2)^2]（2a^2-1/2）
=(a^2-a+1/4+a^2+a+1/4)(2a^2-1/2)
=(2a^2+1/2)(2a^2-1/2)
=4a^4-1/4

(a+2b-3)(a+2b+3)
=[(a+2b)-3][(a+2b)+3]
=(a+2b)^2-3^2
=a^2+4ab+4b^2-9

(x^2+x+3)(x^2-x-3)
=[x^2+(x+3)][x^2-(x+3)]
=x^4-(x+3)^2
=x^4-x^2-6x-9

(x+2y+3)^2-（x-2y+3)(x-2y-3)
=[(x+2y)+3]^2-[(x-2y)+3][(x-2y)-3]
=(x+2y)^2+6(x+2y)+9-(x-2y)^2+9
=[(x+2y)^2-(x-2y)^2]+6(x+2y)+18
=(x+2y+x-2y)(x+2y-x+2y)+6x+12y+18
=2x*4y+6x+12y+18
=8xy+6x+12y+18

哎,我也不会!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!