- 先化简,再求值:(a-3)(a+3)-a(a-6),其中a=5.
- 对于任意整数n,多项式(n+7)2-n2都能被( )A.2整除B.n整除C.7整除D.n+7整除
- (2x+1)(-2x+1)的计算结果是( )A.4x2+1B.1-4x2C.1+4x2D.-4x2-1
- 计算:(-23m+n)(-23m-n)=______.
- 计算(2x-3y+1)(2x+3y-1)的结果是( )A.4x2-12xy+9y2-1B.4x2-9y2-6y-1C.4x2+9y2-1D.4x2-9y2+6y-1
- 已知a2+b2=5,(3a-2b)2-(3a+2b)2=-48,则a+b=______.
- 计算:①(2+1)(2-1)=______;②(3+2)(3-2)=______;③(2+3)(2-3)=______;④(
- 求证:当n是整数时,两个连续奇数的平方差(2n+1)2-(2n-1)2是8的倍数.
- (-a+1)(a+1)(a2+1)等于( )A.a4-1B.a4+1C.a4+2a2+1D.1-a4
- 计算:(-a+b)(-a-b)=______.
- “两个连续正整数的平方差(较大数的平方减去较小的平方)等于这两个连续整数的和.”这个判断正确吗?试着用你学过的知识说明...
- 计算:(1)(x-2y)(x+2y)-(x+2y)2(2)(a+2b+3c)(a+2b-3c)
- (-5a2+4b2)( )=25a4-16b4,括号内应填( )A.5a2+4b2B.5a2-4b2C.-5a2-4b2D.-5a2+4b2
- 若a2-b2=20,a+b=5,则ab=______.
- 2012=______,48×52=______.