上海市各区2018届九年级中考二模数学试卷精选汇编计算题专题宝山区、嘉定区19．（本题满分10分）先化简，再求值：2x x+13+-x2-4x+22-x，其中x=2+3.19.解：原式=2x x+13++…………2分(x-2)(x+2)x+2x-2=2x+(x+1)(x-2)+3(x+2)(x-2)(x+2)………………………1分x2+4x+4 =…………………………………………2分(x-2)(x+2)(x+2)2=………………………2分(x-2)(x+2)=x+2x-2…………………………………………1分把x=2+3代入x+22+3+2得：原式=………………1分x-22+3-2=43+1………………………………1分3长宁区19．（本题满分10分）1x+3x2+4x+3先化简，再求值：，其中x=x+1x2-1x2-2x+11 2+1-÷= 1- ⨯ 131 x + 3 ( x - 1)219. （本题满分 10 分）解：原式=(3 分)x + 1 ( x + 1)( x - 1) ( x + 3)( x + 1)x - 1-(2 分)x + 1 ( x + 1)2 ==x + 1 - x + 1 ( x + 1)22( x + 1)2(1 分)(1 分)当 x =1 2 2 2= 2 - 1 时，原式= = = =1 (3 分)2 + 1 ( x + 1)2 ( 2 - 1 + 1) 2 ( 2)2崇明区19．（本题满分 10 分）1计算： 27 + ( 3 - 2)2 + 9 2 - (π - 3.14)019．（本题满分 10 分）解：原式 = 3 3 + 7 - 4 3 + 3 - 1 ……………………………………………………8 分= 9 - 3…………………………………………………………………2 分奉贤区19．（本题满分 10 分）1计算： ( 2 - 1)2 + + 8 2- ( )-1．3 + 2319、 3 - 2 ；黄浦区)+(2018-20180-3-23.) ()⎛1⎫-2计算：tan45-2sin60+12- ⎪．2（19．（本题满分10分）计算：(22+231219．解：原式=12+1-23-3—————————————————————（6分）=23+1-23+3————————————————————————2分）=4—————————————————————————————（2分）金山区1o o⎝2⎭19．解：原式=1-2⨯32+23-4……………………………………………（8分）=3-1+23-4……………………………………………（1分）=33-5．………………………………………………………（1分）静安区19．（本题满分10分）计算：18+(-cot45 )2018+2-3+(π-3)0-(sin30 )-1．19．（本题满分10分）计算：18+(-cot45 )2018+2-3+(π-3)0-(sin30 )-1．1解：原式=32+(-1)2018+(3-2)+1-()-1…………………（5分）2=32+1+3-2+1-2…………………………（3分）=22+3…………………………………（2分）计算：1x(x+2)2(x+2)(x-2)=x-5-2-(-3)0+（）-1．闵行区19．（本题满分10分）12+1+(-1)-2018-2cos45o+83．19．解：原式=2-1+1-2+2……………………………………（2分+2分+2分+2分）=2．……………………………………………………………………（2分）普陀区19．（本题满分10分）先化简，再求值：x+2x2+4x+4x-2÷-x x2x2-4，其中x=2-2.x+2x2x-219．解：原式=·················································（3分）1-·····································································（2分）x+2x+2x-1=.··············································································（1分）x+2当x=2-2时，原式=2-2-12-2+2························································（1分）=2-32.2青浦区19．(本题满分10分)=2-32····························································（1分）1计算：52+12⎪÷ 2 (x + 3)2 ， ····························································· （5 分）20．(本题满分 10 分)先化简，再求值：⎛ x - 2 -⎝5 ⎫ （x +3）x + 2 ⎭ x + 2，其中 x = 3 ．19．解：原式= 5+ 5 - 2 - 1 + 2 ． ································································ （8 分）= 2 5 - 1 ．20．解：原式= x 2 - 4 - 5 x + 2 ⨯ x + 2=(x + 3)(x - 3)x + 2⨯ x + 2(x + 3)2 ， ······················································· （1 分）= x - 3x + 3. ·················································································· （1 分）当 x = 3 时，原式=松江区19．（本题满分 10 分）3 - 3 3 + 3= 3 - 2 .计算： 30 - 1 - 3 +19．（本题满分 10 分）13 + 2+ 8 ．计算： 30 - 1 - 3 + 13 + 2+ 8 ．解：原式=1 - ( 3 - 1) + 3 - 2 + 2 2 ……………………………（每个 2 分）= 2 + 2 ……………………………………………………………2 分徐汇区19.计算：12-(1)-1+213-1-(π-3.14)0+|23-4|.杨浦区19、（本题满分10分）先化简，再求值：。