数学七年级

显示全部楼层 · 2011-3-24 22:09:10

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

千问 · 2011-3-24 22:09:10

704×696=（700+4）（700-4）=700^2-16=.489984(x+2y)(x-2y)+(x+1)(x-1)=x^2-4y^2+x^2-1=2x^2-4y^2-1x(x-1)-(x-1/3)(x+1/3)=x^2-x-(x^2-1/9)=1/9-x(2m+3)(2m-3)=4m^2-9x(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

千问 · 2011-3-24 22:09:10

704×696=7002-42=4900-16=4884(x+2y)(x-2y)+(x+1)(x-1)=x2-4y2+x2-1=2x2-4y2-1x(x-1)-(x-1/3)(x+1/3)=x2-x-x2+1/9= - x+1/9(2m+3)(2m-3)=4

千问 · 2011-3-24 22:09:10

704*696=（700+4）*（700-4）=490000-16=489984(x+2y)(x-2y)+(x+1)(x-1)=x^2-4y^2+x^2-1=2x^2-4y^2-1x(x-1)-(x-1/3)(x+1/3)=x^2-x-x^2+1/9=1/9-x(2m+3)(2m-3)=4m^2-9x(x+1)+(2-x)(2+x

千问 · 2011-3-24 22:09:10

704×696=（700+4）（700-4）=490000-16=489984(x+2y)(x-2y)+(x+1)(x-1)=x2-4y2+x2-1=2x2-4y2-1x(x-1)-(x-1/3)(x+1/3)=x2-x-(x2-1/9)=-x+1/9(2m+3)(2m-3)=

千问 · 2011-3-24 22:09:10

704×696=(700+4)*(700-4)=700^2-4^2=490000-8=489992这样？

数学 七年级

数学七年级