七年级数学合并同类项同步练习(附答案)

合并同类项 一、选择 1 ．计算的结果是( ) A. B. C. D. 2 ．下面运算正确的是( ). A. B. C. D. 3 ．下列计算中,正确的是( ) A、2a+3b=5ab; B、a3-a2=a; C、a2+2a2=3a2; D、(a-1)0=1. 4 ．已知一个多项式与的和等于,则这个多项式是( ) A. B. C. D. 5 ．下列合并同类项正确的是 A. B. C. D. 6 ．下列计算正确的是( ) (A)3a+2b=5ab (B)5y2-2y2=3 (C)-p2-p2=-2p2 (D)7m-m=7 7 ．加上-2a-7等于3a2+a的多项式是 ( ) A、3a2+3a-7 B、3a2+3a+7 C、3a2-a-7 D、-4a2-3a-7 8 ．当 时, 的值为( ) A. 5050 B. 100 C. 50 D. -50 二、填空题 9 ．化简: _________. 10．计算: _________｡ 11．一个多项式与2x2-3xy的差是x2+xy,则这个多项式是_______________. 三、解答题 12．求多项式:10X3-6X2+5X-4与多项式-9X3+2X2+4X-2的差｡ 13．化简:2(2a2+9b)+3(-5a2-4b) 14．化简: . 15．先化简,后求值. (1)化简: (2)当 时,求上式的值. 16．先化简,再求值: x2 + (-x2 +3xy +2y2)-(x2-xy +2y2),其中x=1,y=3. 17．计算:(1) ; (2)5(m-n)+2(m-n)-4(m-n)｡ 18．先化简,再求值: ,其中 , . 19．化简求值: ,其中 . 20．先化简,后求值: ,其中 21．化简求值: ,其中 22．给出三个多项式: , , ; 请你选择其中两个进行加法或减法运算,并化简后求值:其中 . 23．先化简,再求值: ,其中 . 24．先化简,再求值｡ (5a2-3b2)+(a2+b2)-(5a2+3b2)其中a=-1 b=1 25．化简求值 (-3x2-4y)-(2x2-5y+6)+(x2-5y-1) 其中 x=-3 ,y=-1 26．先化简再求值:(ab-3a2)-2b2-5ab-(a2-2ab),其中a=1,b=-2｡ H:\fanwen caiji two\让企业文化的阳光洒落在基层.doc 27．有这样一道题:“计算 的值,其中 , ｡”甲同学把“ ”错抄成了“ ”但他计算的结果也是正确的,请你通过计算说明为什么? 28．已知: ,求 的值｡ 3.4合并同类项参考 一、选择题 1 ．B 2 ．B; 3 ．C; 4 ．A 5 ．D 6 ．C 7 ．B 8 ．D 二、填空题 9 ． ; 10．-2x 11．3x2-2xy 三、解答题 12．粘贴有误，原因可能为题目为公式编辑器，而没有其它字符 13．解:原式=4a2+18b-15a2-12b =-11a2+6b 14．解:原式= =-xy 15．原式= = . 16．x2 + (-x2 +3xy +2y2)-(x2-xy +2y2) = x2-x2 +3xy +2y2-x2+xy-2y2 = 4xy-x2 当x=1,y=3时 4xy-x2=4×1×3-1=11｡ 17．(1) (2)5(m-n)-2(m-n)-4(m-n) =(5-2-4)(m-n) =-2(m-n) =-2m+2n｡ 18．解:原式= = = 当 ,y=2时,原式=4 . 19．解: 原式= 20．原式 ,当 时,原式 ; 21．原式= ;-2; 22．(1) ( )+( )= (去括号2分) 当 ,原式= (2)( )-( ) = (去括号2分) 当 ,原式= ( )+( )= ( )-( )= ( )+( )= ( )-( )= 23．解:原式 当 时,原式= =0 24．解:原式=5a2-3b2+a2+b2-5a2-3b2 =-5b2+a2 当a=-1 b=1原式=-5×12+(-1)2=-5+1=-4 25．33． 26． -8 27．解:∵原式= ∴此题的结果与 的取值无关｡ 28．解:原式= = = = ∵ , 又∵ ∴ , ∴原式= =3 _1102890575.unknown _1103176338.unknown _1103176427.unknown _1112105349.unknown _1138904862.unknown _1138904948.unknown _1138904949.unknown _1161603691.unknown _1161603699.unknown _1166191929.unknown _1166191970.unknown _1191962386.unknown _1191962393.unknown _1191962410.unknown _1191962427.unknown _1233259145.unknown _1233259146.unknown _1233259147.unknown _1233259186.unknown _1233259190.unknown _1233259202.unknown _1233259298.unknown _1233259478.unknown _1233341220.unknown _1233341231.unknown _1233341277.unknown _1233341301.unknown _1233341484.unknown _1233341527.unknown _1233341615.unknown _1233341682.unknown _1233341767.unknown _1233342562.unknown _1233342730.unknown _1233342783.unknown _1233342931.unknown _1243624797.unknown _1244033481.unknown _1244034171.unknown _1253560186.unknown _1253560425.unknown _1253560812.unknown _1253560836.unknown _1253560899.unknown _1253779120.unknown _1253779926.unknown _1253780637.unknown _1253780887.unknown _1257691557.unknown _1257691558.unknown _1257691559.unknown _1257691560.unknown _1257691561.unknown _1257692267.unknown _1257692268.unknown _1257692269.unknown _1257692270.unknown _1257692271.unknown _1257692318.unknown _1257692319.unknown _1257692320.unknown _1257692321.unknown _1257692322.unknown _1257692344.unknown _1257692345.unknown _1257692346.unknown _1260185402.unknown _1260185936.unknown _1260186076.unknown _1260186091.unknown _1260186259.unknown _1260186284.unknown _1260186320.unknown _1260186380.unknown _1260964526.unknown _1260964571.unknown _1260964602.unknown _1260964702.unknown _1261832377.unknown _1261832511.unknown _1261838593.unknown _1275209237.unknown _1291919276.unknown _1291922055.unknown _1291922099.unknown _1291922109.unknown _1291922574.unknown _1291922582.unknown _1291922591.unknown _1293175252.unknown _1293175696.unknown _1293447596.unknown _1293447597.unknown