Question

数学 七年级 下册

用平方差公式进行计算
704×696=
(x+2y)(x-2y)+(x+1)(x-1)=
x(x-1)-(x-1/3)(x+1/3)=
(2m+3)(2m-3)=
x(x+1)+(2-x)(2+x)=
(3x-y)(3x+y)+y(x+y)=
(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)=
要过程

Answer 1

704×696=(700+4)×(700-4)=700^2-4^2=489984
(x+2y)(x-2y)+(x+1)(x-1)=x^2-4y^2+x^2-1=2x^2-4y^2-1
(2m+3)(2m-3)=4m^2-9
x(x+1)+(2-x)(2+x)=x^2+x+4-x^2=x+4
(3x-y)(3x+y)+y(x+y)=9x^2-y^2+xy+y^2=9x^2+xy
(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)=[(a^2-1)/4b^2]-9a^2+4b^2
这么多选我吧~

Answer 2

704×696=（700+4）×（700-4）=700^2-4^2=490000-16=489984
(x+2y)(x-2y)+(x+1)(x-1)=(x^2-4y^2)+(x^2-1)=2x^2-4y^2-1
x(x-1)-(x-1/3)(x+1/3)=x^2-x-x^2+1/9=1/9-x
(2m+3)(2m-3)=4m^2-9
x(x+1)+(2-x)(2+x)=x^2+x+4-x^2=x+4
(3x-y)(3x+y)+y(x+y)=9x^2-y^2+xy+y^2=9x^2+xy
(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)=a^2-1/4b^2-9a^2+4b^2=-8a^2+15/4b^2

Answer 3

的是