1、若有错,请改正:(1)a2-(2a-b+c) =a2-2a-b+c; (2)-(x-y)+(xy-1) =-x-y+xy-1. (3)(yx) 2 =(xy) 2 (4) (yx) 2 =(xy) 2 (5) (yx)3 =(xy) 3 4.化简:(1)(2x-3y)+(5x+4y); (2)(8a-7b)-(4a-5b);(3)a-(2a+b)+2(a-2b); (4)3(5x+4)-(3x-5);(5)(8x-3y)-(4x+3y-z)+2z; (6)-5x2+(5x-8x2)-(-12x2+4x)+2;(7)2-(1+x)+(1+x+x2-x2); (8)3a2+a2-(2a2-2a)+
2、(3a-a2)。1.根据去括号法则,在_上填上“+”号或“-”号:(1) a_(-b+c)=a-b+c; (2)a_(b-c-d)=a-b+c+d;(3) _(a-b)_(c+d)=c+d-a+b2.已知x+y=2,则x+y+3= ,5-x-y= .3.去括号:(1)a+3(2b+c-d); (2)3x-2(3y+2z).(3)3a+4b-(2b+4a); (4)(2x-3y)-3(4x-2y).(1)2a-3b+4a-(3a-b); (2)3b-2c-4a+(c+3b)+c.C1. 化简2-2(x+3y)-3(x-2y)的结果是( ).Ax+2;Bx-12y+2;C-5x+12y+2;D2-
3、5x.2. 已知:+=3,求x-x2-(1-x)-1的值.第7课时 去括号(1)1下列各式中,与abc的值不相等的是 ( )Aa(bc) Ba(bc) C(ab)(c) D(c)(ba)2化简0(2pq)的结果是 ( ) A2pq B2pq C2pq D2pq3下列去括号中,正确的是 ( ) Aa(2b3c)a2b3c Bx3(3x22x1)x33x22x1 C2y2(2y1)2y22y1 D(2xy)(x2y2)2xyx2y24去括号: a(bc) ; (ab)(cd) ; (ab)(cd) ; 5x33x2(x1) 5判断题 (1)x(yz)xyz ( ) (2)(xyz)xyz ( )
4、(3)x2(yz)x2yz ( ) (4)(ab)(cd)abcd ( )6去括号:(2m3); n3(42m); (1) 16a8(3b4c); (2) (xy)(pq);(3)8(3a2ab4); (4) 4(rnp)7(n2q)(5)8 (yx) 2 (xy) 2 4(yx) 2 3(xy) 2+2(yx) 2 7先去括号,再合并同类项:2n(3n1); a(5a3b)(2ba); 3(2s5)6s; 1(2a1)(3a3); 3(ab2a)(3ab); 14(abc2a)3(6a2abc)8把 a(bc)去括号后的结果应为 ( )Aabc Babc Cabc Dabc9化简(3)3的结果为 ( )A6 B2 C26 D6210先去括号,再合并同类项:6a22ab2(3a2ab); 2(2ab)4b(2ab)9a36a22(a3a2) ; 2 tt(t2t3)2 (2t23t1)11对a随意取几个值,并求出代数式253a11aa107(1a)的值,你能从 中发现什么?试解释其中的原因、