合并同类项、去括号试题
1.合并下列各式中的同类项
(1)3x 2-1-2x-5+3x-x 2 (2)4xy-3y 2-3x 2+xy-3xy-2x 2-4y 2 (3) (4)222b ab a 4
3ab 21a 32-++-
(5)5(a-b)2-7(a-b)+3(a-b)2-9(a-b) (6)3x n+1-4x n-1+12x n+1+32x n-1+5x n -2x n
(7)3a -(4b -2a +1)
(8)x -[(3x +1)-(4-x )]
(9)-4x +3(31
x -2)
(10)(3x-5y)-(6x+7y)+(9x-2y)
(11)2a-[3b-5a-(3a-5b)]
(12)323722+-++a a a a
(13)5(43)(3)a b a a b +---+
(14)222(25)(32)2(41)a a a -+-----
(15)(531)(21)x x y x y +-+--+
(16)()232a a b a ---????
(17)8(2)4(3)2x y x y z z --+-+
(18)[]{}23(2)2a b a b a a -----
(19)8x +2y +2(5x -2y )
(20)(x 2-y 2)-4(2x 2-3y 2)
(21)-3(2x 3y -3x 2y 2+3xy 3)
(22)(-4y +3)-(-5y -2) +3y
(23)(6x 2-x +3)-2(4x 2+6x -2
(24){}222234(3)x x x x x ??--+--??
(25)11(46)3(22)32
a a
b
c c b ---+-+ (26)[](43)(3)()5x y y x x y x ----+--
(27)22121232a a b a b ????--++-+ ? ?????
(28) 2-[2(x+3y)-3(x-2y)]
(29)(2m-3)+m-(3m-2) (30)3(4x-2y )-3(-y+8x ).
(31)(2x-3y)+(5x+4y) (32)(8a-7b)-(4a-5b)
(33)a-(2a+b)+2(a-2b) (34)3(5x+4)-(3x-5)
(35)(8x-3y)-(4x+3y-z)+2z (36)-5x
2+(5x-8x 2)-(-12x 2+4x)+2
(37)2-(1+x)+(1+x+x 2-x 2) (38)3a
2+a 2-(2a 2-2a)+(3a-a 2)
(39)2a-3b+[4a-(3a-b)]
(40)3b-2c-[-4a+(c+3b)]+c
(41)x-(3x-2)+(2x-3)
(42)(3a 2+a-5)-(4-a+7a 2)
(43)x 2+(-3x-2y+1)
(44)x-(x 2-x 3+1)
(45)3a+4b-(2b+4a)
(46)(2x-3y)-3(4x-2y)
(47)(2x-3y)+(5x+4y) (48)(8a-7b)-(4a-5b)
(49)a-(2a+b)+2(a-2b) (50)3(5x+4)-(3x-5)
(51)(8x-3y)-(4x+3y-z)+2z (52)-5x
2+(5x-8x 2)-(-12x 2+4x)+2
(53)2-(1+x)+(1+x+x 2-x 2) (54)3a
2+a 2-(2a 2-2a)+(3a-a 2)
(55)5a +(3x -3y -4a) (56)3x -(4y -2x +1)
(57)7a +3(a +3b ) (58)(x 2-y 2)-4(2x 2-3y )
(59)2a -3b +[4a -(3a -b)] (60)3b -2c -[-4a +(c +3b)]+c
(61)x+[x+(-2x-4y)] (62) (a+4b)- (3a-6b)
(63)3x 2-1-2x-5+3x-x 2 (64) -0.8a 2b-6ab-1.2a 2b+5ab+a 2
b
(65) 222b ab a 43ab 21a 32-++- (66) 6x 2y+2xy-3x 2y 2-7x-5yx-4y 2x 2-6x 2y
(67) 8x +2y +2(5x -2y) (68) 3a -(4b -2a +1)
(69) 7m +3(m +2n) (70) (x 2-y 2)-4(2x 2-3y 2)
(71) -4x +3(3
1x -2) (72) 5(2x-7y)-3(4x-10y)
(73))153()52(+---y x y x (74) )56(3)72(2+--x x
(75))3(2)2(322b ab ab a +--- (76)
)3
123()322(2122y x y x x +-+--
(77) )]12(45[3---x x x (78) 2xy-{5x-3[xy-31x(y+1)]-4xy}
2.求下列代数式的值:3m 2+-3m 2,其中m=6, n=2。
3、如果关于字母x 的代数-3x 2+mx+nx 2-x+10的值与x 的取值无关,求m 、n 的值.
4、已知2x 2+xy=10,3y 2+2xy=6,求4x 2+8xy+9y 2的值.
5、已知:|x-y-3|+(a+b+4)2
=0,求)(22)(3)(2b a b a x y y x +-+---。 6、化简求值.
(1)5a 3-2a 2+a -2(a 3-3a 2)-1,a =-1.
(2)4a 2b -[3ab 2-2(3a 2b -1)],其中a =-,b =1。
7.已知x 2+xy =2,y 2+xy =5,求x 2+2xy +y 2的值.
8.已知:A +B =3x 2+x ,B +C =x 2,求A -C 的值.
9.已知x+y=6,xy=-4,求: (5x-4y-3xy)-(8x-y+2xy)的值。 10.先化简,再求值
(1)2211312()()2323x x y x y --+-+其中22,3
x y =-=。 (2)7x 2y -xy -[3x 2y -2(4xy 2 -21xy )]-4x 2y ,其中x=-21,y=21。 (3)已知42+--y x x 与互为相反数,求代数式
2223()5()3()()4()3()x y x y x y y x x y y x -----+--++-的值。
11、已知4433m n x y x y +-与是同类项,求代数式10099(3)m n mn +--的值。
12.求代数式-2(x 2+4)+5(x +1) -(4x 2-2x)(其中 x= -2)的值。
13.化简求值:
(1) 9x +6x 2-(x -3
2x 2) ,其中 x=-2。 (2)3a 2-2(2a 2+a )+2(a 2-3a ),其中a=-2; (3)(9a 2-12ab+5b 2)-(7a 2+12ab+7b 2),其中a=
12,b=-12. 14.把多项式x 5-3x 3y 2-3y 2+3x 2-y 5写成两个整式的和,使其中一个只含5次项.
15.把多项式3x 2-2xy-y 2-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.
16. 已知x 2-xy=8, xy-y 2=3,分别求下列各式的值: (1) x 2- y 2 (2)x 2-2xy+y 2
17. 先化简下列各式,再求值:
(1) 3a 2b-{2a 2b+[9a 2b-(6a 2b+4a 2)]-(3a 2b-8a 2)},其中3,21-==
b a . (2) 已知A=2a 2-a, B=-5a+1, 求当21=
a 时,3A-2B+1的值.
2、合并同类项 (1)4x+2y —5x —y (2)—3ab+7—2a 2—9ab —3 (3)x+[x+(-2x-4y)]; (4) (a+4b)- (3a-6b) (5)3x 2-1-2x-5+3x-x 2 (6)-0.8a 2b-6ab-1.2a 2b+5ab+a 2b (7)222b ab a 43 ab 21 a 32-++- (8)6x 2y+2xy-3x 2y 2-7x-5yx-4y 2x 2-6x 2y (9)8x +2y +2(5x -2y ) (10)3a -(4b -2a +1) (11)7m +3(m +2n ) (12)(x 2-y 2)-4(2x 2-3y 2) (13)3x 2-1-2x-5+3x-x 2 (14)4xy-3y 2-3x 2+xy-3xy-2x 2-4y 2 (15)-0.8a 2b-6ab-1.2a 2b+5ab+a 2b (15)222b ab a 43 ab 21 a 32 -++- (16)5(a-b)2-7(a-b)+3(a-b)2-9(a-b) (17)3x n+1-4x n-1+12x n+1+3 2x n-1+5x n -2x n (18)3x 2-1-2x-5+3x-x 2 (19)-0.8a 2b-6ab-1.2a 2b+5ab+a 2b (20) 222b ab a 43 ab 21 a 32 -++- (21)6x 2y+2xy-3x 2y 2-7x-5yx-4y 2x 2-6x 2y (22)4x 2y-8xy 2+7-4x 2y+12xy 2-4; (23)a 2-2ab+b 2+2a 2+2ab - b 2. (24)3x 2-1-2x-5+3x-x 2 (25)-0.8a 2b-6ab-1.2a 2b+5ab+a 2b (26) 222b ab a 43 ab 21 a 32 -++- (27)6x 2y+2xy-3x 2y 2-7x-5yx-4y 2x 2-6x 2y (28)4x 2y-8xy 2+7-4x 2y+12xy 2-4; (29)a 2-2ab+b 2+2a 2+2ab - b 2.
1.根据去括号法则,在上填上“+”号或“-”号: 2. (1) a (-b+c)=a-b+c; (2) a (b-c-d)=a-b+c+d; (3) (a-b) (c+d)=c+d-a+b; 2.已知x+y=2,则x+y+3= , 5-x-y= . 3.下列去括号有没有错误?若有错,请改正: (1)a2-(2a-b+c) (2)-(x-y)+(xy-1) =a2-2a-b+c; =-x-y+xy-1. 4.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) = (5)a+(b-c)=(6)a-(-b+c)= (7)(a+b)+(c+d)=(8)-(a+b)-(-c-d)= (9)(a-b)-(-c+d)=(10)-(a-b)+(-c-d)= (11)a+(-b+c-d)= (12)a-(-b+c-d)= (13)-(p+q)+(m-n)= (14)(r+s)-(p-q)= 5.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)+(3a-a2) (9)5a+(3x-3y-4a) (10)3x-(4y-2x+1) (11)7a+3(a+3b) (12)(x2-y2)-4(2x2-3y) (13) (a+4b)- (3a-6b) (14)3x2-1-2x-5+3x-x2(15) -0.8a2b-6ab-1.2a2b+5ab+a2b