北师大初二数学书习题2.5.1至4题答案 .
北师大初二数学书习题2.5.1至4题答案 .
感激不尽 .
感激不尽 .
数学人气:663 ℃时间:2020-05-19 11:06:44
优质解答
习题2.5 1.(1)x2y2-2xy+1=(xy-1)2; (2)9-12t+4t2=(3-2t)2; (3)y2+y+ =(y+ )2; (4)25m2-80 m +64=(5 m-8)2; (5) +xy+y2=( +y)2; (6)a2b2-4ab+4=(ab-2)2 2.(1)(x+y)2+6(x+y)+9 =[(x+y)+3]2 =(x+y+3)2; (2)a2-2a(b+c)+(b+c)2 =[a-(b+c)]2 =(a-b-c)2; (3)4xy2-4x2y-y3 =y(4xy-4x2-y2) =-y(4x2-4xy+y2) =-y(2x-y)2; (4)-a+2a2-a3 =-(a-2a2+a3) =-a(1-2a+a2) =-a(1-a)2.3.设两个奇数分别为x、x-2,得 x2-(x-2)2 =[x+(x-2)][x-(x-2)] =(x+x-2)(x-x+2) =2(2x-2) =4(x-1)
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