初一数学题

显示全部楼层 · 2013-3-17 14:05:18

(1)(m-2n)^2-(n-2m)^2=m^2-4mn+4n^2-n^2+4mn-4m^2=-3m^2+3n^2(2)(3a+1)^2-(3a+1)(-1+3a)=9a^2+6a+1+3a-9a^2+1-3a=6a+2(3)(x-1)(x+1)(x^2+1)-x(x^3-1)=(x^2-1)(x^2+1)-x(x^3-1)=x^4-1-x^4+x=x-1(4)(a^2+b)(-b+a^2)-(-a)^2(-a^2)=a^4-b^2-a^4=-b^2(5)(a-b+c)(a+b-c)=a^2-(b-c)^2=a^2-b^2+2bc-c^2(6)(-x)^2(x^2+2x-1)-(1-x)(x^3-2x)=x^4+2x^3-x^2-x...

千问 · 2013-3-17 14:05:18

1)原式=m2-4mn+4n2-n2+4mn-4m2=3n2-3m22)原式=(3a+1)((3a+1)-(-1+3a))=(3a+1)2=6a+23)原式=（x2-1)(x^2+1)-x(x^3-1)=x^4-1-(x^4-x)=x-14)原式=(a^2+b)...

千问 · 2013-3-17 14:05:18

1)3n^2-3m^2
2)6a+2 3)x-1
4)2a^4-b^2 5)a^2-b^2-c^2+2bc
6)2x^4+x^3-3x^2+2x
7)2a^4-a^2-b^28)0
9)9y^2
10)405200011、-10x^2+x+2
-912、(a+b)^2+(a-b)^2=2...