（人教通用）2019年中考数学总复习 第一章 数与式 第3课时 分式知能优化训练.doc

第3课时分式知能优化训练中考回顾1.(xx浙江金华中考)若分式x-3x+3的值为0,则x的值为()A.3B.-3C.3或-3D.0答案A2.(xx北京中考)如果a-b=23,那么代数式a2+b22a-baa-b的值为()A.3B.23C.33D.43答案A3.(xx山东滨州中考)若分式x2-9x-3的值为0,则x的值为.答案-34.(xx甘肃张掖中考)计算:ba2-b2aa-b-1.解原式=b(a+b)(a-b)aa-b-a-ba-b=b(a+b)(a-b)a-a+ba-b=b(a+b)(a-b)a-bb=1a+b.5.(xx山东滨州中考)先化简,再求值:(xy2+x2y)xx2+2xy+y2x2yx2-y2,其中x=0-12-1,y=2sin 45-8.解原式=xy(x+y)x(x+y)2(x+y)(x-y)x2y=x-y.当x=1-2=-1,y=2-22=-2时,原式=2-1.模拟预测1.使分式x-2(x-1)(x-2)有意义,x应满足的条件是()A.x1B.x2C.x1或x2D.x1,且x2答案D2.如图,电路的总电阻为10 ,若R1=2R2,则R1,R2的值分别是()A.R1=30 ,R2=15 B.R1=203,R2=103C.R1=15 ,R2=30 D.R1=103,R2=203答案A3.化简a+3a-4a-31-1a-2的结果等于()A.a-2B.a+2C.a-2a-3D.a-3a-2答案B4.若ab=2,则a2-ab+b2a2+b2的值等于()A.45B.1C.35D.2答案C5.若代数式2x-1-1的值为零,则x=.答案36.若x+y=1,且x0,则x+2xy+y2xx+yx的值为.答案17.化简并求值:1x-y+1x+y2x-yx2-y2,其中x,y满足|x-2|+(2x-y-3)2=0.解原式=2x(x-y)(x+y)(x-y)(x+y)2x-y=2x2x-y.|x-2|+(2x-y-3)2=0,|x-2|=0,(2x-y-3)2=0.x=2,y=1.原式=2222-1=43.8.化简求值:x+1x2-1+x+1x-12-x-5x-1x-1,其中x是不等式3x-22x+12的最大整数解.解原式=x+1(x+1)(x-1)+x+1x-1(2-x)(x-1)-(5x-1)x-1=1x-1+x+1x-1-x2-2x-1x-1=1x-1+x+1x-1x-1-(x+1)2=1x-1-1x+1=2x2-1,解不等式3x-22x+12得x3,该不等式的最大整数解为x=2,当x=2时,原式=222-1=23.