去括号练习题
1.去掉下列各式中的括号.
(1)(a+b)-(c+d)=________; (2)(a-b)-(c-d)=________;
(3)(a+b)-(-c+d)=_______; (4)-[a-(b-c)]=________.
2.下列去括号过程是否正确?若不正确,请改正.
(1)a-(-b+c-d)=a+b+c-d. ( )______________
(2)a+(b-c-d)=a+b+c+d. ( )______________
(3)-(a-b)+(c-d)=-a-b+c-d.( )______________
3.在下列各式的括号内填上适当的项.
(1)x-y-z=x+( )=x-( );
(2)1-x2+2xy-y2=1-( );
(3)x2-y2-x+y=x2-y2-( )=(x2-x)-( ).
4.下列去括号中,正确的是( )
A.a2-(2a-1)=a2-2a-1 B.a2+(-2a-3)=a2-2a+3
C.3a-[5b-(2c-1)]=3a-5b+2c-1 D.-(a+b)+(c-d)= -a-b-c+d
5.下列去括号中,错误的是( )
A.a2-(3a-2b+4c)=a2-3a+2b-4c; B.4a2+(-3a+2b)=4a2+3a-2b
C.2x2-3(x-1)=2x2-3x+3; D.-(2x-y)-(-x2+y2)= -2x+y+x2-y2
6.不改变代数式a-(b-3c)的值,把代数式括号前的“-”号变成“+”号,•结果应是( )
A.a+(b-3c) B.a+(-b-3c) C.a+(b+3c) D.a+(-b+3c)
7.化简下列各式并求值:
(1)x-(3x-2)+(2x-3); (2)(3a2+a-5)-(4-a+7a2);
(3)3a2-2(2a2+a)+2(a2-3a),其中a=-2;
(4)(9a2-12ab+5b2)-(7a2+12ab+7b2),其中a= 1,b=-2 .
8.把多项式x5-3x3y2-3y2+3x2-y5写成两个整式的和,使其中一个只含5次项.
9.把多项式3x2-2xy-y2-x+3y-5分成两组,两个括号间用“-”号连接,并且使第一个括号内含x项.