Question

(1). (-x-2)(x-2) (2). x^2-(x-1)^2 (3). (a+2/1)^2-(a-2/1)^2 (4). (-x-1)(x+1) 运用乘法公式计算

求解答 要过程 是4个题哦！

Answer 1

前三个题都用平方差公式{ a²-b²=(a+b)(a-b) }，最后一个用完全平方公式{ (a+b)²=a²+2ab+b² }

1 =-(x+2)(x-2) 2 =(x+x-1)(x-x+1) 3 =(a+½+a-½)(a+½-a+½) 4 =-(x+1)(x+1)
=-（x²-4) =2x-1 =2a =-(x²+2x+1)
=4-x² =-x²-2x-1

Answer 2

即
(1).(-x-2)(x-2)
=[-(x+2)](x-2)
=-(x²-4)
=4-x²

(2). x^2-(x-1)^2
=[x-(x-1)][x+(x-1)]
=(2x-1)

(3). (a+2/1)^2-(a-2/1)^2
=[(a+1/2)+(a-1/2)][(a+1/2)-(a-1/2)]
=2a×1
=2a

(4). (-x-1)(x+1)
=[-(x+1)](x+1)
=-(x²+2x+1)
=-x²-2x-1