★1化简及求值滚动集训
化简及求值滚动集训类型一整式的化简及求值1.计算:a(a+2b)-(a+b)(a-b)解:原式=a2+2ab-a2+b2=2ab+b2.2.计算:(x+2y)2-(x+y)(x-y).解:原式=x2+4xy+4y2-x2+y2=4xy+5y2.3.先化简,再求值:(x+2)(x-2)+x(1-x),其中x=-1.解:原式=x2-4+x-x2=x-4.当x=-1时,原式=-1-4=-5.4.先化简,再求值池(a十跖)一(tz+1)2十2口,其中a=42+1=施一匚解:原式=+2必一(於十2a+l)十2&=iz2Jr2aba22al+2a2ab17半a=jj2+1=a/21时原式=2(施+1)(芒一1)1=21=1.5.已知:x2-y2=12,x+y=3,求2x2-2xy的值.解:x2-y2=12,(x+y)(x-y)=12.«x+y=3,.x-y=4,.+,得2x=7.2x2-2xy=2x(x-y)=7X4=28.类型二分式的化简及求值6.化简:Q了+鸟)宁.7.先化简,再求值:(总-"斗警,其中I.解:原式=三1x1卜1(比+)(兀一)_(t+1)2工+1/当x=2时,原式=y-8先化简,再求值:丁;-乞+19其中攵=/1一(*)1_11a/3|.to百卡_z2(h+1)(h1)解:原式一可匸口一=0(?J+lrr+1_1<r+l'当x=/12-(y)1-11-V3|=273-2+1-73=原式=原式=731+19先化简,再求值22力一*x22xy-y老十盘'其中x=l,y=2.龈rg-u(r+y)Cy)Q|力解:原式Q_y)2zQ+切+«zp=yI工y工_$=&+,工刃当x=l9y=2时,原式=当x=l9y=2时,原式=1+21-210.先化简(1_)十乂疋丫丁',然后从一2=无=2的范围内选取一个合适的整数作为乂的值代入求值.解:原式=三(无+1)(无一1)_工十U-2)2=尸尢满足一2WzW2且为整数,若使分式有意义山只能取0,-2.*当工=0时9>!=(当X=2时9原式=+).