七年级上册《整式加减》计算题强化训练试题
1.合并同类项:
(1)3a -5a +6a. (2)x 2y +4x 2y -6x 2y.
(3)-3mn 2+8m 2n -7mn 2+m 2n. (4)2x 3-6x -6x 3-2+9x +8.
2.合并同类项:
(1)5x 2
-5.5x +4-3x 2
+4x -3;
(2)23a 2-12ab +3
4a 2+ab -b 2;
(3)32ab 2-4.5ab 3-3
2ab 2+4.5b 3a -8a 3b 2+8a 2b 3;
(4)194a 2+52ab -283b 2+54a 2+236ab -34b 2.
3.合并同类项:
(1)2x 2-3x +4x 2-6x -5;
(2)a 2-2ab +2ba -3a +5+2a.
4.先化简,再求值:
(1)3x 2+2xy -4y 2-3xy +4y 2-3x 2.其中x =3
2,y =2;
(2)-5m 2n +4mn 2-2mn +6m 2
n +3mn.其中m =-12,n =3.
5.先化简,再求值:
(1)-12x 3y 2-94xy +12x 3y 2+11
4xy -x 3y -5+x 3y ,其中|x -1|+(y +2)2=0;
(2)14(a +b)2+9(a +b)-(a +b)-1
2(a +b)2+5(a +b),其中a +b =2.
6.先去括号,再合并同类项:
(1)3a-(4b-2a+1);
(2)3(x2y-xy2)-4(2x2y-3xy2).
7.先化简,再求值:3(x2-xy-2y)-2(x2-3y),其中x=-1,y=2.
8.化简:4a2-3a+3-3(-a3+2a+1).
9.先化简,再求值:4xy-[(x2+5xy-y2)-2(x2+3xy-1
2
y2)],
其中x=-1,y=2.
10.计算:
(1)5a-(2a-4b);
(2)(2x2y-4xy2)-(1
2
xy2+x2y);
(3)2(x-x2+1)-3(x2+x);
(4)3a2-[5a-(1
2
a-3)+2a2].
11.若A=x2-2xy+y2,B=x2-y2,求:(1)A+B;(2)A-B.
12.先化简,再求值:-2(-x2+5+4x)-(2x2-4-5x),其中x=-2.
13.计算:
(1)(6m2+4m-3)+2(2m2-4m+1);
(2)4(2x2-3x+1)-2(4x2-2x+3);
(3)5a+(4b-c)-3(a+3b-2c);
(4)3x2-[5x-(1
2
x-3)+3x2].
14.先化简,再求值:
(1)2(x +x 2
y)-2
3
(6x 2y +3x)-y ,其中x =1,y =3;
(2)3x 2y -[2xy 2-2(xy -32x 2y)]+3xy 2-xy ,其中|x -2|+(y +1
2)2=0.
15.计算:-3(2a 2-2ab)+4(a 2+ab -6);
16.先化简,再求值:2(x 2y +xy 2-1)-2(x 2y -1)+2xy 2-1,其中x =2,y =-1
2.
17.先化简,后求值
(1)()()ab b a b a 245352323+++-,其中2
1,1=-=b a
(2)1]242[6422+y x xy xy y x )--(
--,其中1,2
1
==y x -.
答 案
1.合并同类项:
(1)3a -5a +6a. (2)x 2y +4x 2y -6x 2y. (3)-3mn 2+8m 2n -7mn 2+m 2n.
(4)2x 3-6x -6x 3-2+9x +8. 解:(1)原式=(3-5+6)a =4a. (2)原式=(1+4-6)x 2y =-x 2y.
(3)原式=(-3-7)mn 2+(8+1)m 2n =-10mn 2+9m 2n. (4)原式=(2-6)x 3+(-6+9)x -2+8=-4x 3+3x +6.
2.合并同类项:
(1)5x 2-5.5x +4-3x 2+4x -3; 解:原式=2x 2-1.5x +1.
(2)23a 2-12ab +3
4a 2+ab -b 2; 解:原式=1712a 2+1
2ab -b 2.
(3)32ab 2-4.5ab 3
-32ab 2+4.5b 3a -8a 3b 2+8a 2b 3; 解:原式=-8a 3b 2+8a 2b 3.
(4)194a 2+52ab -283b 2+54a 2+236ab -34b 2.
解:原式=6a 2+193ab -12112
b 2
.
3.合并同类项:
(1)2x 2-3x +4x 2-6x -5;
解:原式=(2x 2+4x 2)+(-3x -6x)-5 =6x 2-9x -5.
(2)a 2-2ab +2ba -3a +5+2a.
解:原式=a 2+(-2ab +2ba)+(-3a +2a)+5 =a 2-a +5.
4.先化简,再求值:
(1)3x 2+2xy -4y 2-3xy +4y 2-3x 2.其中x =3
2,y =2;
解:原式=(3x 2-3x 2)+(2xy -3xy)+(4y 2-4y 2) =-xy.
当x =32,y =2,原式=-3
2×2=-3.
(2)-5m 2n +4mn 2-2mn +6m 2n +3mn.其中m =-1
2,n =3.
解:原式=m 2n +4mn 2+mn. 当m =-1
2
,n =3时,
原式=(-12)2×3+4×(-12)×32+(-12)×3=-75
4.
5.先化简,再求值:
(1)-12x 3y 2-94xy +12x 3y 2+11
4xy -x 3y -5+x 3y ,其中|x -1|+(y +2)2=0;
解:由题意,得x -1=0,y +2=0,所以x =1,y =-2. 原式=1
2
xy -5,当x =1,y =-2时,原式=-6.
(2)14(a +b)2+9(a +b)-(a +b)-1
2(a +b)2+5(a +b),其中a +b =2. 解:原式=-1
4(a +b)2+13(a +b).
当a +b =2时,原式=-1
4×4+13×2=25.
6.先去括号,再合并同类项: (1)3a -(4b -2a +1); 解:原式=5a -4b -1. (2)3(x 2y -xy 2)-4(2x 2y -3xy 2). 解:原式=-5x 2y +9xy 2.
7.先化简,再求值:3(x 2-xy -2y)-2(x 2-3y),其中x =-1,y =2. 解:原式=3x 2-3xy -6y -2x 2+6y =x 2-3xy. 当x =-1,y =2时,原式=(-1)2-3×(-1)×2=7. 8.化简:4a 2-3a +3-3(-a 3+2a +1). 解:原式=4a 2-3a +3+3a 3-6a -3 =3a 3+4a 2+(-3a -6a)+(3-3) =3a 3+4a 2-9a.
9.先化简,再求值:4xy -[(x 2
+5xy -y 2
)-2(x 2
+3xy -12
y 2
)],其中x =-1,y
=2.
解:原式=4xy -(x 2
+5xy -y 2
-2x 2
-6xy +y 2
) =4xy -(-x 2-xy) =x 2+5xy ,
当x =-1,y =2时,原式=x 2+5xy =(-1)2+5×(-1)×2=-9.
10.计算:
(1)5a-(2a-4b);解:原式=5a-2a+4b =3a+4b.
(2)(2x2y-4xy2)-(1
2
xy2+x2y);
解:原式=x2y-9
2
xy2.
(3)2(x-x2+1)-3(x2+x);解:原式=-5x2-x+2.
(4)3a2-[5a-(1
2
a-3)+2a2].
解:原式=3a2-5a+1
2
a-3-2a2
=a2-9
2
a-3.
11.若A=x2-2xy+y2,B=x2-y2,求:(1)A+B;(2)A-B.
解:(1)A+B=x2-2xy+y2+x2-y2=2x2-2xy.
(2)A-B=(x2-2xy+y2)-(x2-y2)=x2-2xy+y2-x2+y2=-2xy+2y2.
12.先化简,再求值:-2(-x2+5+4x)-(2x2-4-5x),其中x=-2. 解:原式=2x2-10-8x-2x2+4+5x=-3x-6,
当x=-2时,原式=6-6=0.
13.计算:
(1)(6m2+4m-3)+2(2m2-4m+1);
解:原式=6m2+4m-3+4m2-8m+2
=10m2-4m-1.
(2)4(2x2-3x+1)-2(4x2-2x+3);
解:原式=8x 2-12x +4-8x 2+4x -6 =-8x -2.
(3)5a +(4b -c)-3(a +3b -2c); 解:原式=5a +4b -c -3a -9b +6c =2a -5b +5c.
(4)3x 2
-[5x -(1
2
x -3)+3x 2].
解:原式=3x 2-(5x -1
2x +3+3x 2)
=3x 2-5x +12x -3-3x 2
=-9
2
x -3.
14.先化简,再求值:
(1)2(x +x 2
y)-23
(6x 2
y +3x)-y ,其中x =1,y =3;
解:原式=2x +2x 2y -4x 2y -2x -y =-2x 2y -y. 当x =1,y =3时, 原式=-2×12×3-3=-9.
(2)3x 2y -[2xy 2-2(xy -32x 2y)]+3xy 2-xy ,其中|x -2|+(y +1
2)2=0.
解:原式=3x 2y -2xy 2+2xy -3x 2y +3xy 2-xy =xy 2+xy.
由题意,得x =2,y =-1
2
.
所以当x =2,y =-12时,原式=2×14+2×(-12)=12-1=-1
2.
15.计算:-3(2a 2-2ab)+4(a 2+ab -6); 解:原式=-6a 2+6ab +4a 2+4ab -24 =-2a 2+10ab -24.
16.先化简,再求值:2(x 2y +xy 2-1)-2(x 2y -1)+2xy 2-1,其中x =2,y =-1
2.
解:原式=2x 2y +2xy 2-2-2x 2y +2+2xy 2-1 =4xy 2-1.
当x =2,y =-12时,原式=4×2×(-12)2
-1=1.
17.先化简,后求值
(1)()()ab b a b a 245352323+++-,其中2
1,1=-=b a =-3/4
(2)1]242[6422+y x xy xy y x )--(
--,其中1,2
1
==y x -.
=-11/4