人教版七年级数学《有理数》计算题专项练习
学校:班级:姓名:得分:1.计算:2(5a2﹣3b)﹣3(a2﹣2b)
2.计算:3a2+2a﹣4a2﹣7a
3. 计算:2(a﹣2b)﹣3(2a﹣b)
4. 计算:5x2﹣[2x﹣3(x+2)+4x2].
5.计算:3x2﹣3(x2﹣2x+1)+4.
6.化简:2(2a2+9b)+(﹣5a2﹣4b).
7.化简:﹣2a+(3a﹣1)﹣(a﹣5).
8.计算:a+2b+3a﹣2b
9. 计算:2(x2y﹣3xy2)﹣3(x2y﹣4xy2)
10.先化简,再求值:(2a2﹣5a)﹣(2a2﹣4a+2),其中a=.11.化简:3(2x2y﹣3xy2)﹣(xy2﹣3x2y).
12.化简:2(3a﹣2b)﹣3(a﹣3b)
13.化简(3m+2)﹣3(m2﹣m+1)+(3﹣6m).
14.化简:﹣2(x2﹣3xy)+6(x2﹣xy)
15.化简:2(2x2﹣4x+1)﹣(3x2﹣2x+5).
16.计算:2x2+(3y2﹣xy)﹣(x2﹣3xy).
17.化简:(5x2﹣2x﹣3)﹣(x﹣4+3x2)
18.先化简,再求代数式的值:2(a2﹣ab)﹣3(a2﹣ab﹣),其中a=2,b=.19.化简求值:2(3x2﹣2x+1)﹣(5﹣2x2﹣7x),其中x=﹣1.
20.先化简,再求值.,其中a=﹣1,b=.
21.已知A=2x2﹣9x﹣11,B=﹣6x+3x2+4,且B+C=A
(1)求多项式C;
(2)求A+2B的值.
22.先化简,再求值:(4a2﹣2a﹣8)﹣(a﹣1),其中a=1.
23.先化简,再求值.(﹣x2+5+4x)+(5x﹣4+2x2),其中x=﹣2.
24.化简后再求值:x+2(3y2﹣2x)﹣4(2x﹣y2),其中x=2,y=﹣1.
25.先化简,再求值:
﹣a2b+(3ab2﹣a2b)﹣2(2ab2﹣a2b),其中a=﹣1,b=﹣2.
26.先化简再求值:3(a2+2b)﹣(2a2﹣b),其中a=﹣2,b=1.
27.小明同学做一道数学题时,误将求“A﹣B”看成求“A+B”,结果求出的答案是3x2﹣2x+5.已知A=4x2﹣3x﹣6.请你帮助小明同学求出A﹣B.
28.先化简,再求值.x﹣2(x﹣y2)+(﹣x+y2),其中x=﹣2,y=.
人教版七年级数学《有理数》计算题专项练习
参考答案与试题解析
1.计算:2(5a2﹣3b)﹣3(a2﹣2b)
【解答】解:原式=10a2﹣6b﹣3a2+6b
=7a2
2.计算:3a2+2a﹣4a2﹣7a
【解答】解:原式=(3﹣4)a2+(2﹣7)
=﹣a2﹣5a;
3. 计算:2(a﹣2b)﹣3(2a﹣b)
【解答】解:原式=2a﹣4b﹣6a+3b
=﹣4a﹣b;
4.计算:5x2﹣[2x﹣3(x+2)+4x2].
【解答】解:原式=5x2﹣(2x﹣x﹣6+4x2)
=5x2﹣2x+x+6﹣4x2
=x2﹣x+6.
5.计算:3x2﹣3(x2﹣2x+1)+4.
【解答】解:3x2﹣3(x2﹣2x+1)+4
=3x2﹣x2+6x﹣3+4
=2x2+6x+1.
6.化简:2(2a2+9b)+(﹣5a2﹣4b).
【解答】解:原式=4a2+18b﹣5a2﹣4b
=﹣a2+14b.
7.化简:﹣2a+(3a﹣1)﹣(a﹣5).
【解答】解:原式=﹣2a+3a﹣1﹣a+5
=4.
8.计算:a+2b+3a﹣2b
【解答】解:(1)原式=4a
9.计算:2(x2y﹣3xy2)﹣3(x2y﹣4xy2)
【解答】解:原式=2x2y﹣6xy2﹣3x2y+12xy2=﹣x2y+6xy2 10.先化简,再求值:
(2a2﹣5a)﹣(2a2﹣4a+2),其中a=.
【解答】解:原式=2a2﹣5a﹣a2+2a﹣1=a2﹣3a﹣1
当a=时,
∴原式=﹣1﹣1=﹣
11.化简:3(2x2y﹣3xy2)﹣(xy2﹣3x2y).
【解答】解:原式=6x2y﹣9xy2﹣xy2+3x2y
=9x2y﹣10xy2
12.化简:2(3a﹣2b)﹣3(a﹣3b)
【解答】解:2(3a﹣2b)﹣3(a﹣3b)
=6a﹣4b﹣3a+9b
=3a+5b.
13.化简(3m+2)﹣3(m2﹣m+1)+(3﹣6m).【解答】解:(3m+2)﹣3(m2﹣m+1)+(3﹣6m)=3m+2﹣3m2+3m﹣3+3﹣6m
=﹣3m2+2.
14.化简:﹣2(x2﹣3xy)+6(x2﹣xy)
【解答】解:原式=﹣2x2+6xy+6x2﹣6xy=4x2.
15.化简:2(2x2﹣4x+1)﹣(3x2﹣2x+5).
【解答】解:2(2x2﹣4x+1)﹣(3x2﹣2x+5)
=4x2﹣8x+2﹣3x2+2x﹣5
=x2﹣6x﹣3.
16.计算:2x2+(3y2﹣xy)﹣(x2﹣3xy).
【解答】解:原式=2x2+3y2﹣xy﹣x2+3xy=x2+3y2+2xy.
17.化简:(5x2﹣2x﹣3)﹣(x﹣4+3x2)
原式=5x2﹣2x﹣3﹣x+4﹣3x2=2x2﹣3x+1;
18.先化简,再求代数式的值:2(a2﹣ab)﹣3(a2﹣ab﹣),其中a=2,b=.【解答】解:原式=2a2﹣ab﹣3a2+3ab+1=﹣a2+2ab+1,
当a=2,b=时,原式=﹣4+2+1=﹣1.
19.化简求值:2(3x2﹣2x+1)﹣(5﹣2x2﹣7x),其中x=﹣1.
【解答】解:原式=6x2﹣4x+2﹣5+2x2+7x=8x2+3x﹣3,
当x=﹣1时,
∴原式=8×1﹣3﹣3=2
20.先化简,再求值.,其中a=﹣1,b=.
【解答】解:原式=﹣2a2b﹣2ab+2a2b=﹣2ab,
当a=﹣1,b=时,原式=+1=.
21.已知A=2x2﹣9x﹣11,B=﹣6x+3x2+4,且B+C=A
(1)求多项式C;
(2)求A+2B的值.
【解答】解:(1)∵B+C=A,
∴C=A﹣B=(2x2﹣9x﹣11)﹣(﹣6x+3x2+4)
=2x2﹣9x﹣11+6x﹣3x2﹣4
=﹣x2﹣3x﹣15;
(2)A+2B=(2x2﹣9x﹣11)+2(﹣6x+3x2+4)
=x2﹣x﹣﹣12x+6x2+8