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+6
题型:单选题难度:简单来源:不详
计算(2x-3y+1)(2x+3y-1)的结果是( )A.4x2-12xy+9y2-1 | B.4x2-9y2-6y-1 | C.4x2+9y2-1 | D.4x2-9y2+6y-1 |
|
答案
(2x-3y+1)(2x+3y-1), =[2x-(3y-1)][2x+(3y-1], =(2x)2-(3y-1)2, =4x2-9y2+6y-1. 故选D. |
举一反三
已知a2+b2=5,(3a-2b)2-(3a+2b)2=-48,则a+b=______. |
计算:①(+1)(-1)=______; ②(+)(-)=______; ③(2+)(2-)=______; ④(+2)(-2)=______. 通过以上计算,观察规律,写出用n(n为正整数)表示上面规律的等式______. |
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.a4-1 | B.a4+1 | C.a4+2a2+1 | D.1-a4 |
|
最新试题
热门考点