2020长沙市中考数学大一轮新素养突破提分专练（一）实数混合运算与代数式的化简求值（含答案）

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1、提分专练(一)实数混合运算与代数式的化简求值|类型1|实数的混合运算1.2019南充计算:(1-)0+|2-3|-12+12-1.2.2019遵义计算:2sin60+|3-2|+(-1)-1-3-8.3.2019益阳计算:4sin60+(-2019)0-12-1-|-23|.4.2019齐齐哈尔计算:13-1+12-6tan60+|2-43|.5.2019济宁计算:6sin60-12+120+|3-2018|.|类型2|整式的化简求值6.2019南京计算:(x+y)(x2-xy+y2).7.先化简,再求值:(x+y)2-y(2x+y),其中x=-2.|类型3|分式的化简求值8.2019重庆A卷

2、计算:a+9-4aa-2a2-9a-2.9.化简:2xyx2-y21x-y+1x+y.10.2019荆门先化简,再求值:a+ba-b22a-2b3a+3b-4a2a2-b23ab,其中a=3,b=2.11.2019鄂州先化简x2-2xx2-4x+4-4x-2x-4x2-4,再从-1,2,3,4中选一个合适的数作为x的值代入求值.12.2019宜昌已知xy,y=-x+8,求代数式x2x-y+y2y-x的值.13.2019枣庄先化简,再求值:x2x2-11x-1+1,其中x为整数且满足不等式组x-11,5-2x-2.14.2019菏泽先化简,再求值:1x-y2yx+y-11y2-x2,其中x=y+

3、2019.【参考答案】1.解:原式=1+3-2-23+2=1-3.2.解:2sin60+|3-2|+(-1)-1-3-8=232+2-3+(-1)-(-2)=3.3.解:4sin60+(-2019)0-12-1-|-23|=432+1-2-23=23+1-2-23=-1.4.解:13-1+12-6tan60+|2-43|=3+23-63+43-2=1.5.解:原式=632-23+1+2018-3=33-23-3+2019=2019.6.解:(x+y)(x2-xy+y2)=x3-x2y+xy2+x2y-xy2+y3=x3+y3.7.解:原式=x2+2xy+y2-2xy-y2=x2.当x=-2时,

4、原式=4.8.解:原式=a2-2a+9-4aa-2a-2a2-9=(a-3)2a-2a-2(a+3)(a-3)=a-3a+3.9.解:原式=2xy(x+y)(x-y)2x(x+y)(x-y)=2xy(x+y)(x-y)(x+y)(x-y)2x=y.10.解:原式=2(a+b)3(a-b)-4ab3(a+b)(a-b)=2(a+b)2-4ab3(a+b)(a-b)=2(a2+b2)3(a+b)(a-b).当a=3,b=2时,原式=2(3+2)3(3+2)(3-2)=103.11.解:原式=x(x-2)(x-2)2-4x-2x-4x2-4=xx-2-4x-2x-4x2-4=x-4x-2(x-2)(

5、x+2)x-4=x+2.x-20,x-40,x2且x4,当x=-1时,原式=-1+2=1.(或当x=3时,原式=3+2=5)12.解:原式=x2x-y+y2y-x=x2x-y-y2x-y=x2-y2x-y=(x+y)(x-y)x-y=x+y.当xy,y=-x+8时,原式=x+(-x+8)=8.13.解:原式=x2(x+1)(x-1)1+x-1x-1=x2(x+1)(x-1)x-1x=xx+1.解不等式组x-11,5-2x-2,得2x72.因为x为整数,所以x=3.代入可得原式=33+1=34.14.解:1x-y2yx+y-11y2-x2=1x-y2y-(x+y)x+y(y+x)(y-x)=-(2y-x-y)=x-y.x=y+2019,原式=y+2019-y=2019.